Mechanisms of Tissue Destruction in Cholesteatoma

描述（申请人提供）：胆脂瘤是起源于鼓膜的上皮肿瘤样生长，通常是慢性中耳炎的后遗症。这种病变的进行性通常通过破骨细胞骨吸收导致中耳和内耳结构的破坏。这种破坏导致听力损失、前庭功能障碍和颅内并发症。目前对这种疾病的治疗仅限于手术根除，必须经常重复手术。慢性感染是胆脂瘤的另一个特征，因此我们对导致破骨细胞激活的炎症信号通路很感兴趣。我们最近确定了一氧化氮合酶1 （NOS1或神经元NOS）在破骨细胞活化中的作用。我们现在希望通过确定NOS1被激活的机制和抑制一氧化氮产生的内源性调节剂来进一步探索这一作用。为此，我们提出了以下具体目标。具体目标1：定位介导破骨细胞活性的NOSl的细胞来源，并定位潜在的内源性NOSl调节剂。具体目标2：确定NOSl的激活机制，并评估各种调节剂在胆脂瘤模型中控制一氧化氮产生和最终破骨细胞骨吸收活性的效率。神经元通过将NOSl与谷氨酸受体的NMDA型连接来控制NOSl的激活。有趣的是，破骨细胞也具有功能性谷氨酸受体，包括NMDA亚型，但其功能尚不清楚。此外，谷氨酸受体拮抗剂抑制破骨细胞封闭骨的能力，这是骨吸收活性的先决条件。NOS1基因靶向缺失小鼠的破骨细胞表现出类似的表型。这一巧合提供了有趣的证据，表明这两个观察结果是相关的，破骨细胞可能使用与神经元相同的机制来调节NOS1的激活。这些研究为胆脂瘤中破骨细胞活性的控制提供了重要的见解，并可能导致药物干预的发展，从而取代手术治疗这种使人衰弱的疾病。

DESCRIPTION (provided by applicant): Cholesteatomas are epithelial tumor-like growths that arise from the tympanic membrane, typically as a sequela of chronic otitis media. The progressive nature of this lesion commonly results in the destruction of middle and inner ear structures via osteoclastic bone resorption. This destruction leads to hearing loss, vestibular dysfunction and intracranial complications. Current management of this disease is limited to surgical eradication, which must often be repeated. Chronic infection is another hallmark of the cholesteatoma and we have therefore been interested in the inflammatory signaling pathways that lead to osteoclast activation. We recently established a role for nitric oxide synthase 1 (NOS1 or neuronal NOS) in osteoclast activation. We now wish to explore this role further by identifying the mechanisms by which NOS1 is activated and the endogenous modulators that keep nitric oxide production in check. To this end, we have outlined the following specific aims. Specific Aim 1: To localize the cellular source(s) of NOSl that mediate osteoclast activity and to also localize potential endogenous modulators of NOSl. Specific Aim 2: To identify the mechanism of activation for NOSl and assess the efficiency by which various modulators can control nitric oxide production and ultimately the bone resorbing activity of osteoclasts in models of cholesteatoma. Neurons control NOSl activation by functionally linking it to the NMDA type of glutamate receptor. Interestingly, osteoclasts also have functional glutamate receptors, including the NMDA subtype, but their function is not well understood. Further, glutamate receptor antagonists inhibit the ability of the osteoclast to seal to the bone, a prerequisite to resorption activity. Osteoclasts from mice with targeted deletions of the NOS1 gene exhibit a similar phenotype. This coincidence offers intriguing evidence that these two observations are related and that osteoclasts may use the same mechanisms that neurons do to modulate NOS1 activation. These studies offer important insight into the control of osteoclast activity in cholesteatoma and may lead to the development of pharmacologic interventions that would replace the need for surgery in the treatment of this debilitating disease.