Protection of Brain Injury from Cyanide Poisoning by Carnosic Acid

描述（由申请人提供）：氰化物中毒是一种潜在的生物恐怖剂，是危及生命的，急性接触会导致缺氧脑损伤，心肺衰竭，并在几分钟到几小时内死亡。这种急性毒性可以用各种解毒剂治疗，但成功与否取决于快速给药和有效渗透各种组织。然而，即使经过治疗，人类急性或慢性氰化物中毒可诱发迟发性神经系统综合征，包括肌张力障碍。典型地，这些患者在数周至数月后表现出帕金森症状，进行性僵硬，主要特征是上肢屈曲和下肢伸展。这些患者的CT和MRI检查一致显示基底神经节病变，包括苍白球和壳核。人类大脑的损伤已经通过尸检得到证实。在急性和慢性氰化物接触后，也报告了类似的观察结果。多种机制被认为是氰化物诱导的神经元损伤的基础，包括抑制细胞色素C氧化酶（CcOX）和生成活性氧（ROS），以响应氰化物诱导的脂质过氧化。对神经元特别有害的是谷氨酸转运功能障碍和离子泵失效，通过过度刺激nmda型谷氨酸受体（NMDARs）导致兴奋性毒性神经元细胞死亡。此外，氰化物诱导NMDAR氧化还原位点的化学还原，这最初是在我们的实验室发现的，并导致NMDAR操作的离子通道的额外激活，Ca2+内流和随之而来的神经元损伤；这些机制的考虑说明了抗氧化剂和NMDAR拮抗剂可以防止氰化物引起的神经元损伤。由于氰化物抑制CcOX和增强NMDARs的毒性作用都集中在氧化应激上，因此开发氰化物中毒的神经保护药物的一个可能策略是寻找能够对抗氧化损伤的低分子量化合物。本研究提出，鼠尾草酸（carnosic acid， CA）是一种来自迷迭香提取物的亲电性化合物，通过Nrf2转录途径，通过血脑屏障上调内源性抗氧化酶，从而达到抑制氰化物对中枢神经系统毒性的潜在对策。我们假设这种亲电化合物在对抗氰化物在大脑中的毒性作用方面比抗氧化分子有优势，因为它们的作用更持久，并通过转录介导的信号通路被放大。我们将通过研究CA在暴露于氰化物的培养神经元和氰化物中毒小鼠模型中的神经保护活性来验证这一假设。本提案的具体目标如下：探讨CA对氰化物中毒体外模型的神经保护作用。具体目标2。在模拟氰化物摄入作用的小鼠体内模型中检验CA的神经保护作用。

DESCRIPTION (provided by applicant): Cyanide poisoning is a potential bioterrorist agent, is life threatening, and acute exposure results in hypoxic brain injury, cardiopulmonary failure, and death within minutes to hours. Such acute toxicity is treatable by various antidotes, but success depends on rapid administration and effective penetration of the various tissues. However, even with treatment, acute or chronic cyanide intoxication in humans can induce a delayed neurological syndrome, including dystonia. Typically, these patients show Parkinsonian symptoms after weeks to months, with progressive rigidity and predominant features of flexed upper limbs and extended lower limbs. CT and MRI examinations of these patients have consistently revealed lesions in the basal ganglia, including the globus pallidus and putamen. Damage in the human brain has been confirmed via autopsy. Similar observations have been reported following both acute and chronic cyanide exposure. Multiple mechanisms are thought to underlie cyanide-induced neuronal damage, including inhibition of Cytochrome C oxidase (CcOX) and generation of reactive oxygen species (ROS) in response to cyanide- induced lipid peroxidation. Particularly harmful to neurons is dysfunctional glutamate transport and ionic pump failure, contributing to excitotoxic neuronal cell death by overstimulation of NMDA-type glutamate receptors (NMDARs). Furthermore, cyanide induces chemical reduction of the redox site(s) of the NMDAR, which were originally discovered in our laboratory, and result in additional activation of NMDAR-operated ion channels, Ca2+ influx, and consequent neuronal damage; these mechanistic considerations account for the fact that anti- oxidants and NMDAR antagonists can prevent cyanide-induced neuronal damage. As both toxic effects of cyanide by inhibition of CcOX and potentiation of NMDARs converge on oxidative stress, one possible strategy for the development of neuroprotective drugs for cyanide poisoning is to search for low-molecular-weight compounds that can counter oxidative damage. Here, as potential countermeasures against CNS toxicity by cyanide, we propose to use carnosic acid (CA), an electrophilic compound from rosemary extract, which crosses the blood-brain-barrier to exert effects by up-regulating endogenous anti-oxidant enzymes via the Nrf2 transcriptional pathway. We hypothesize that such electrophilic compounds have an advantage over antioxidant molecules for counteract the toxic effect of cyanide in brain because their action is more sustained and amplified by transcription-mediated signaling pathways. We will test this hypothesis by investigating the neuroprotective activity of CA in culture neurons exposed to cyanide and in a mouse model of cyanide poisoning. Specific Aims of this proposal are as follows: Specific Aim 1. To investigate neuroprotective effects of CA in an in vitro model of cyanide poisoning. Specific Aim 2. To examine neuroprotective effects of CA in an in vivo mouse model mimicking the effects of cyanide ingestion.