Institute of Pharmaceutical Innovation, Hubei Province Key Laboratory of Occupational Hazard Identification and Control, School of Medicine, Wuhan University of Science and Technology, Wuhan 430065, China.
Demonstration Center for Experimental Basic Medicine Education, Wuhan University Taikang Medical School (School of Basic Medical Sciences), Wuhan, Hubei 430071, China.
Bone. 2024 Dec;189:117261. doi: 10.1016/j.bone.2024.117261. Epub 2024 Sep 18.
Glucocorticoids (GCs) are extensively used as anti-inflammatory and immunosuppressive medications in the long-term treatment of rheumatic disorders, respiratory diseases, renal diseases, and organ transplantation. Prolonged use of GCs can reduce bone mineral density, leading to osteoporosis (Glucocorticoid Induced Osteoporosis, GIOP) and fracture. All-trans retinoic acid (ATRA) is an active vitamin A metabolite that regulates embryonic development and adult organ function. ATRA has been found in studies to enhance osteogenesis. To examine the interventional effects of ATRA on GIOP and the mechanisms of ATRA activities, we first performed bioinformatic analysis to identify potential gene targets of ATRA. Zebrafish larvae were recruited as experimental animals, and the frequently used GC, prednisolone, was administered to larvae to construct a GIOP model. We evaluated the influence of exogenous ATRA on the activities of bone metabolic enzymes, the expression of genes linked to osteoblasts and osteoclasts, and the restoration of bone mineral density and bone mass in GIOP zebrafish larvae. Furthermore, we studied the influence of RBM14, a transcriptional coactivator and negative reciprocal factor of ATRA, on the regulation of osteoblastic gene expression during the anti-GIOP process of ATRA using the morpholino knockdown approach. The findings of bone metabolic enzyme activity (alkaline phosphatase, ALP and tartrate-resistant acid phosphatase, TRAP) and expression assays of osteoblastic marker genes (Runx2a, Runx2b, SP7, Csf1a, RANKL, and CTSK) indicated that ATRA had bidirectional effects on osteogenesis. However, in the GIOP model, ATRA reversed the GIOP-induced osteoporosis phenotype by inhibiting the GIOP-induced suppression of osteoblastic metabolic enzyme (ALP) activities and osteoblastic marker gene expression (Runx2a, Runx2b, and SP7), and this antagonism was concentration-dependent. We also observed that ATRA inhibited RBM14 expression in zebrafish larvae, while ATRA alone and RBM14 knockdown showed a consistent induction of osteoblast marker gene expression, implying that ATRA's inhibitory effect on RBM14 expression may underlie ATRA's osteogenic effects. Based on these data, we postulated that ATRA may ameliorate GIOP by decreasing RBM14 expression, thereby enhancing osteoblastic marker gene expression.
糖皮质激素（GCs）在风湿性疾病、呼吸系统疾病、肾脏疾病和器官移植的长期治疗中被广泛用作抗炎和免疫抑制药物。GC 的长期使用会降低骨密度，导致骨质疏松症（糖皮质激素诱导的骨质疏松症，GIOP）和骨折。全反式视黄酸（ATRA）是一种调节胚胎发育和成人器官功能的活性维生素 A 代谢物。研究发现，ATRA 可增强成骨作用。为了研究 ATRA 对 GIOP 的干预作用及其 ATRA 活性的机制，我们首先进行了生物信息学分析，以确定 ATRA 的潜在基因靶点。我们招募斑马鱼幼虫作为实验动物，并向幼虫中给予常用的 GC 泼尼松龙，构建 GIOP 模型。我们评估了外源性 ATRA 对骨代谢酶活性、与成骨细胞和破骨细胞相关的基因表达以及 GIOP 斑马鱼幼虫骨密度和骨量恢复的影响。此外，我们使用 morpholino 敲低方法研究了转录共激活因子和 ATRA 的负反馈因子 RBM14 对 ATRA 抗 GIOP 过程中成骨基因表达调节的影响。骨代谢酶活性（碱性磷酸酶，ALP 和抗酒石酸酸性磷酸酶，TRAP）和成骨标记基因（Runx2a、Runx2b、SP7、CSF1a、RANKL 和 CTSK）的表达测定表明，ATRA 对成骨作用具有双向影响。然而，在 GIOP 模型中，ATRA 通过抑制 GIOP 诱导的成骨代谢酶（ALP）活性和成骨标记基因表达（Runx2a、Runx2b 和 SP7）的抑制作用，逆转了 GIOP 诱导的骨质疏松表型，这种拮抗作用呈浓度依赖性。我们还观察到 ATRA 在斑马鱼幼虫中抑制 RBM14 的表达，而 ATRA 单独作用和 RBM14 敲低均表现出一致的成骨标记基因表达诱导，这表明 ATRA 对 RBM14 表达的抑制作用可能是 ATRA 成骨作用的基础。基于这些数据，我们推测 ATRA 可能通过降低 RBM14 的表达来改善 GIOP，从而增强成骨标记基因的表达。
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