ETHANOL AND OSTEOBLASTOGENESIS: ROLES OF IL-1 AND TNF

描述(由申请人提供)：流行病学数据表明，过量饮酒每年可能会给美国经济造成20亿美元的骨骼病理损失。酒精性骨病患者表现出明显的骨形成障碍。酒精可能通过增加细胞因子的分泌间接改变骨代谢，细胞因子被证明是绝经后骨质疏松症的关键因素。已有研究表明，细胞因子通过增加骨吸收和减少骨形成来调节雌激素缺乏所致的骨丢失。此外，临床研究表明，细胞因子在酒精性肝病中过度产生。 牵张成骨(DO)是一种延长骨的临床和实验方法，已被用于分离和研究慢性乙醇暴露对膜内(直接成骨细胞形成)骨形成的影响，膜内骨形成组织良好，在空间上有别于吸收过程。 以往的工作表明，慢性乙醇暴露大鼠(肠内营养模型)降低了胫骨的弯曲强度，抑制了DO时的骨形成，并增加了肝脏和DO间隙中肿瘤坏死因子α(TNF)的表达。此外，在DO过程中使用肿瘤坏死因子拮抗剂可以防止乙醇对骨抑制作用，而在DO过程中使用肿瘤坏死因子治疗可以抑制骨形成。将一种新的小鼠DO模型与液体乙醇注射相结合的初步结果表明，慢性乙醇暴露降低了DO期间的胫骨强度并抑制了骨形成。在这个小鼠模型中，与大鼠相似，在DO过程中使用肿瘤坏死因子拮抗剂保护骨形成，而外源性肿瘤坏死因子抑制骨形成。 本项目的具体目的是确定1)肿瘤坏死因子作用的下游介体，2)细胞色素P450 2E1(细胞色素P450 2E1)的作用，以及3)活性氧自由基(ROS)在乙醇诱导肿瘤坏死因子中的作用。目前的研究假设是乙醇诱导的细胞色素P450_2E_1增加ROS，产生肿瘤坏死因子，肿瘤坏死因子与特定的受体结合，触发抑制骨形成的信号转导通路。 这项研究的长期目标是支持未来在将酒精或细胞因子过量作为危险因素的患者的骨科手术中进行药理学和/或营养干预。

DESCRIPTION (provided by applicant): Epidemiological data suggest that excessive alcohol consumption may cost the US economy $2 billion annually in skeletal pathology. Patients with alcoholic bone disease display marked impairment in bone formation. Alcohol may alter bone metabolism indirectly by elevating the secretion of cytokines shown to be critical factors in postmenopausal osteoporosis. It has been demonstrated that cytokines mediate bone loss due to estrogen deficiency by increasing bone resorption and decreasing bone formation. Furthermore, clinical studies show that cytokines are over-produced in alcohol-induced liver disease. Distraction osteogenesis (DO) is a clinical and experimental procedure for lengthening bones that has been used to isolate and study the effects of chronic ethanol exposure on intramembranous (direct osteoblastogenesis) bone formation, which is well organized and spatially distinct from resorptive processes. Previous work demonstrates that chronic ethanol exposure in the rat (enteral nutrition model) decreases tibial bending strength, inhibits bone formation during DO, and increases the expression of Tumor Necrosis Factor alpha (TNF) in the liver and DO gap. Further, treatment with TNF antagonists during DO prevents osteoinhibiton by ethanol, while treatment of control rats with TNF during DO inhibits bone formation. Preliminary results, combining a novel murine DO model with liquid ethanol delivery, demonstrate that chronic ethanol exposure decreases tibial strength and inhibits bone formation during DO. In this murine model, analogous to the rat, TNF antagonist treatment during DO protects bone formation and exogenous TNF inhibits bone formation. The Specific Aims of this project are to determine 1) the downstream mediators of TNF actions, 2) the roles of cytochrome p450 2E1 (CYP2E1) and 3) the role of reactive oxygen species (ROS) in ethanol's induction of TNF. The working hypotheses are that ethanol induction of CYP2E1 increases ROS, inducing TNF, which binds to a specific receptor and triggers signal transduction pathways that inhibit bone formation. The long term goals of this research are to support future pharmacological and/or nutritional interventions in orthopaedic procedures in patients with ethanol or cytokine excess as risk factors.