Mechanism of Diabetic Enteric Neuropathy

糖尿病（DM）是一种常见疾病，在美国有1550万患者患病（1）。在 2007年，DM引起的并发症花费了美国医疗保健系统580亿美元（1）。一个主要的并发症 DM是神经病。便秘是肠神经病的一个关键后果， 在糖尿病患者中常见，患病率为60%，而在一般人群中为15%。DM相关 肠神经病由高血糖诱导的神经元凋亡引起。然而， 糖尿病中高血糖驱动神经元凋亡的机制仍是个谜。鉴于人们日益认识到 Toll样受体（TLR）在驱动各种慢性疾病过程中的作用，特别是那些 与氧化应激和晚期糖基化产物（AGEs）相关，已知AGEs是由 由于高血糖，我们假设TLR在DM相关的肠神经病变中起作用。为支持这一 我们已经观察到一种特定TLR，即TLR 4的上调与 高血糖诱导的神经元凋亡。此外，TLR 4的遗传和药理学消除防止了 高血糖诱导的神经元凋亡和DM相关的结肠动力障碍。因此我们 假设高血糖诱导TLR 4活化导致神经元凋亡， 因此，驱动与DM相关的结肠动力障碍。为了验证假设， 为了探讨高血糖诱导神经细胞凋亡的机制，我们将进行 建立TLR 4介导高血糖诱导的肠神经元凋亡的作用的实验， 阐明所涉及的机制。使用来自WT/TLR 4-/-小鼠的原代肠神经元和敲 在我们实验室开发的肠神经元细胞系中的下调/过表达策略，我们将建立 TLR 4在调节高血糖诱导的肠神经元损伤中的必要性和充分性。的 高血糖诱导的TLR 4激活的机制将被检查，重点是高级 糖化终产物（AGES）和氧化应激。此外，我们将表征信号事件 参与高血糖诱导的TLR 4激活肠神经元凋亡，集中在下游 TLR 4的靶点，包括NF-B。最后，我们将确定TLR 4对肠神经元凋亡的作用， 体内结肠动力障碍。我们的初步数据表明，链脲佐菌素（STZ）诱导的DM导致 肠神经元凋亡和小鼠结肠肌间神经元损失。这些变化得到改善， TLR 4-/- DM小鼠。总之，这些研究不仅将阐明一种新的机制，涉及TLR 4在肿瘤细胞中的作用。 高血糖诱导的肠神经元凋亡的发病机制，但也提供了“原则证明”， 可用于治疗或预防与DM相关的运动障碍的靶向治疗。

DM mellitus (DM) is a common disorder with a prevalence of 15.5 million sufferers in the United States (1). In 2007, complications arising from DM cost the US healthcare system $58 billion (1). One major complication of DM is neuropathies. Constipation is a key consequence of enteric neuropathy and is significantly more common in DM patients with a prevalence of 60% compared to 15% in the general population. DM-associated enteric neuropathy results from hyperglycemia-induced neuronal apoptosis. However, the mechanism by which hyperglycemia drives neuronal apoptosis in DM remains enigmatic. In light of the increasing appreciation of the role of toll-like receptors (TLR) in driving a variety of chronic disease processes, especially those associated with oxidative stress and advanced glycation products (AGEs), which is known to result from hyperglycemia, we hypothesized that TLRs play a role in DM-associated enteric neuropathy. In support of this notion, we have observed that upregulation of one particular TLR, namely TLR4 is associated with hyperglycemia-induced neuronal apoptosis. Moreover, genetic and pharmacological ablation of TLR4 prevents both hyperglycemia-induced neuronal apoptosis and DM-associated colonic dysmotility. Thus, we hypothesize that hyperglycemia-induced activation of TLR4 results in neuronal apoptosis and, consequently, drives the colonic dysmotility associated with DM. To test the hypothesis and further investigate the underlying mechanism(s) of hyperglycemia-induced neuronal apoptosis, we will perform experiments to establish the role of TLR4 in mediating hyperglycemia-induced enteric neuronal apoptosis and elucidate the mechanism involved. Using primary enteric neurons from WT/TLR4-/- mice and knock down/overexpression strategies in the enteric neuronal cell line developed in our laboratory, we will establish the necessity and sufficiency of TLR4 in modulating hyperglycemia-induced enteric neuronal damage. The mechanism of hyperglycemia induced TLR4 activation will be examined focusing on the role of Advanced Glycation end products (AGES) and oxidative stress. Further, we will characterize the signaling events involved in hyperglycemia-induced TLR4 activation in enteric neuronal apoptosis focusing on the downstream targets of TLR4 including NF-¿B. Finally, we will determine the role of TLR4 on enteric neuronal apoptosis and colonic dysmotility in vivo. Our preliminary data indicate that streptozotocin (STZ) -induced DM results in enteric neuronal apoptosis and loss of mouse colonic myenteric neurons. These changes are ameliorated in TLR4-/- DM mice. Taken together these studies will not only elucidate a novel mechanism involving TLR4 in the pathogenesis of hyperglycemia-induced enteric neuronal apoptosis but also provide "proof of principle" for targeted therapies that could be used for the treatment or prevention of dysmotility associated with DM.