Neuropeptides in the pathogenesis of neurocysticercosis

描述(申请人提供)：脑囊虫病(NCC)是一种由猪带绦虫引起的对人类中枢神经系统的寄生性感染。NCC被认为是世界范围内癫痫发作的主要原因。NCC的癫痫发作是由大脑中对濒临死亡的寄生虫产生的局部肉芽肿反应引起的。癫痫发作的介质尚不清楚，在NCC中发现癫痫介质(S)可能导致使用特定的拮抗剂治疗。神经肽P物质(SP)刺激肉芽肿生长和Th1细胞因子的产生。另一种神经肽，生长抑素，刺激Th2细胞因子的产生，并削弱肉芽肿的形成。SP可引起神经元癫痫样反应，而生长抑素具有抗惊厥作用。根据退行性寄生虫的组织学表现，我们将与鼠囊虫病相关的肉芽肿分为4个阶段。早期肉芽肿表达Th1细胞因子和SP，而Th2细胞因子和生长抑素仅在晚期肉芽肿中表达。初步结果还表明，将早期肉芽肿提取物注入大鼠脑内，可引起大鼠的行为惊厥和海马区活动增加。预先给予SP受体拮抗剂可抑制上述作用。同样，大鼠脑内注射SP也可诱发癫痫发作，改变大鼠海马神经元的活动，而这种改变可被SP受体拮抗剂或生长抑素预先完全阻断。我们推测SP介导和生长抑素抑制NCC的肉芽肿性反应和癫痫发作。具体目的1：验证SP和生长抑素调节囊虫病肉芽肿反应的假说。将比较感染、野生型小鼠、SP基因敲除小鼠(SP KO)、SP受体KO小鼠和生长抑素KO小鼠的肉芽肿大小、Th1/Th2和促炎细胞因子水平。具体目的2：确定SP和生长抑素是否分别参与NCC癫痫发作反应的调节和调节。将在NCC癫痫患者的脑活检组织中检测SP蛋白的表达。感染的SP KO和生长抑素KO小鼠的肉芽肿提取物将与野生型小鼠的致痫活性进行比较。具体目标3：确定NCC的癫痫发作是否直接由SP引起和/或间接由SP诱导的细胞因子引起。早期肉芽肿提取物的致痫活性将在SP、IL-1β、TNF-α或IL-6被抑制或阻断的情况下进行测试。此外，还将测试受感染的IL-1β、肿瘤坏死因子-α或IL-6基因敲除的早期肉芽肿的致痫活性。具体目的4：验证生长抑素抑制NCC癫痫发作的假说。将研究早期肉芽肿提取物是否含有生长抑素类似物或SOM拮抗剂的致痫活性。这些研究将确定SP和SOM在NCC发病机制中的重要性，并可能导致未来使用SP拮抗剂和SOM类似物作为抗癫痫药物来治疗NCC和其他癫痫相关疾病的癫痫发作。

DESCRIPTION (provided by applicant): Neurocysticercosis (NCC) is a parasitic infection of the human central nervous system caused by the helminth Taenia solium. NCC is recognized as a leading cause of seizures worldwide. Seizures in NCC are evoked by localized granulomatous responses to dying parasites in the brain. The mediators of the seizures are unknown, identification of seizure mediator(s) in NCC may result in treatment with specific antagonists. The neuropeptide substance P (SP) stimulates granuloma growth and Th1 cytokine production. Another neuropeptide, somatostatin, stimulates Th2 cytokine production and impairs granuloma formation. SP evokes epileptiform responses in neurons, whereas, somatostatin has anticonvulsant properties. We divided granulomas associated with murine cysticercosis into 4 stages based on the histologic appearance of the degenerating parasite. Early stage granulomas expressed Th1 cytokines and SP, whereas Th2 cytokines and somatostatin were only expressed in later stages. Preliminary results also noted that behavioral seizures and increased hippocampal activity were induced when extracts from early granulomas were injected into brain of rats. Pretreatment with SP receptor antagonist inhibited these effects. Similarly, injection of SP into rat brain also induced seizures and altered hippocampal activity that was completely blocked by pretreatment with SP receptor antagonist or somatostatin. We hypothesize that SP mediates and somatostatin inhibits the granulomatous response and seizures in NCC. Specific aim 1: To test the hypothesis that SP and somatostatin modulate granulomatous responses in cysticercosis. Granuloma size, Th1/Th2 and pro-inflammatory cytokine levels in infected, wildtype mice, SP knockout mice (SP KO), SP receptor KO mice and somatostatin KO mice will be compared. Specific aim 2: To determine if SP and somatostatin are respectively responsible for the mediation and modulation of seizure responses in NCC. SP protein expression will be examined in brain biopsies from NCC patients with seizures. Epileptogenic activity of granuloma extracts from infected, SP KO and somatostatin KO mice will be compared to that from wildtype mice. Specific aim 3: To determine if seizures in NCC are directly due to SP and/or indirectly due to SP induced cytokines. Epileptogenic activity of early granuloma extracts will be tested with or without inhibition or blocking of SP, IL-1beta, TNF-alpha or IL-6. Also epileptogenic activity of early granulomas from infected IL-1beta, TNF-alpha or IL-6 knockouts will be tested. Specific aim 4: To test the hypothesis that somatostatin inhibits seizures in NCC. Epileptogenic activity of early granuloma extracts with or without somatostatin analogues or SOM antagonist will be studied. These studies will determine the importance of SP and SOM in pathogenesis of NCC, and may lead to future use of SP antagonist and SOM analogues as anti-epileptic agents for treatment of seizures in NCC and other seizure related diseases.