ROLE OF CASPASE-2 IN OSTEOCOLAST APOPTOSIS AGE-EePENDENT OSTEOPOROSIS

骨是一个活的器官，通过成骨细胞和 破骨细胞对现存骨骼的吸收。高龄时骨质丢失会导致骨质疏松症。 Caspase-2是一种参与细胞程序性死亡(细胞凋亡)的蛋白酶。在上一次资助期间 期间，我们发现caspase-2是衰老动物骨量的重要调节因子。我们的关键人物 观察发现，老年(24-26个月)caspase-2基因缺失小鼠的增龄性骨丢失更为严重 与同龄野生型小鼠相比，差异有统计学意义。这项建议的目的是进一步研究 衰老骨骼中的caspase-2。我们的假设是caspase-2介导了线粒体依赖性的细胞凋亡。 老化的破骨细胞，这是由体内氧化应激诱导的。缺乏caspase-2活性导致 减少老化破骨细胞的凋亡，导致骨吸收增加。为了验证这一假设，首先， 我们将比较老年caspase-2基因缺失和野生型小鼠的骨形成和骨吸收速度 表明caspase-2影响骨吸收。接下来，我们将比较老化破骨细胞的凋亡率 增强/降低抗氧化能力，表明氧化应激是自发性疾病的原因 衰老破骨细胞的凋亡。然后，我们将比较caspase-2(-/-)和(+/+)衰老的凋亡率 破骨细胞研究表明caspase-2在衰老的自发性细胞凋亡中起重要作用 破骨细胞。最后，我们将比较老化的破骨细胞的凋亡率 抗氧化活性和caspase-2活性显示caspase-2是氧化应激诱导的介质 细胞凋亡。钙调蛋白依赖的激酶II(CaMK II)可磷酸化原天冬氨酸蛋白酶-2并阻止 它的激活。NADPH，为各种生化反应提供还原当量以清除 氧化剂也通过增强CaMK II功能来抑制原天冬氨酸氨基转移酶-2的激活。基于这些 结果，我们将验证氧化应激通过以下途径激活老化破骨细胞中caspase-2的假设 通过检测NAPDH水平和CaM和CaM的氧化水平下调NADPH/CaMK II活性 骨质疏松症是影响老年人的一种严重疾病。的主要战略和机制 目前抗骨质疏松治疗的作用是诱导破骨细胞凋亡。因此，这项研究将脱离 破骨细胞凋亡机制研究与抗骨质疏松新途径 治疗。

Bone is a living organ that is maintained through continuous formation of new bone by osteoblasts and resorption of exiting bone by osteoclasts. Loss of bone mass at advanced ages causes osteoporosis. Caspase-2 is a protease that is involved in programmed cell death (apoptosis). During the last funding period, we found that caspase-2 is an important regulator of bone mass in aging animals. Our critical observation was that aging-associated bone loss in old (24-26 month) caspase-2 null mice was more severe than that in the same age wild type mice. The objective of this proposal is to further study the role of caspase-2 in aging skeleton. Our hypothesis is that caspase-2 mediates mitochondrial-dependent apoptosis of aging osteoclasts, which is induced by oxidative stress in vivo. Lack of caspase-2 activity results in reduced apoptosis of aging osteoclasts, leading to increased bone resorption. To test this hypothesis, first, we will compare the rate of bone formation and bone resorption in old caspase-2 null and wild type mice to show that caspase-2 affects bone resorption. Next, we will compare the apoptosis rate in aging osteoclasts that have increased/decreased antioxidant capacity to show that oxidative stress is a cause of spontaneous apoptosis of aging osteoclasts. Then, we will compare the apoptosis rate of caspase-2 (-/-)and (+/+) aging osteoclasts to show that caspase-2 plays an important role in the spontaneous apoptosis of aging osteoclasts. Finally, we will compare the apoptosis rate in aging osteoclasts that have both altered antioxidant activity and caspase-2 activity to show that caspase-2 is a mediator of oxidative stress-induced apoptosis. Calmodulin (CaM) dependent kinase II (CaMK II) can phosphorylate procaspase-2 and prevent its activation. NADPH, which provides reducing equivalent for various biochemical reactions to scavenge oxidants, also inhibits the activation of procaspase-2 by enhancing CaMK II function. Based on these findings, we will test the hypothesis that oxidative stress activates caspase-2 in aging osteoclasts through down-regulation of NADPH/CaMK II activity by examining the level of NAPDH and oxidation of CaM and CaMK II. Osteoporosis is a serious disease that affects the elderly. The main strategy and mechanism of action of current anti-osteoporosis therapy is to induce osteoclast apoptosis. Therefore, this study will shed the light on the mechanism of apoptosis in osteoclasts and open new avenues for new anti-osteoporosis therapies.