Biology of Prion Protein and the TSE Diseases

Pron病或传染性海绵状脑病是人和动物的传染性神经退行性疾病。Prion病的一个主要特征是将正常的宿主蛋白Prion蛋白(PrP)折叠和聚集成疾病相关的蛋白酶抵抗形式(PrPres)，这可能会导致脑损伤。我们先前记录了瘙痒病感染后脑内神经炎性反应的分子细节。 在2017财年，我们用他汀类药物治疗瘙痒病感染的小鼠，试图减少神经炎症并延长生存时间。在以前的研究中，用1型他汀类药物、辛伐他汀或普伐他汀治疗瘙痒病感染的小鼠，显示出对存活时间的微小有益影响。在目前的研究中，为了提高他汀类药物的治疗效果，我们用阿托伐他汀治疗感染的小鼠，阿托伐他汀是一种2型他汀类药物，已经改善了许多1型他汀类药物的药代动力学。进行辛伐他汀或普伐他汀治疗的对比试验。我们评估了瘙痒病感染小鼠的PrPres积聚、神经胶质增生、神经炎症和直到需要安乐死的晚期临床疾病的时间。所有三种他汀类药物都将小鼠的血清总胆固醇降低了40%。然而，在他汀类药物治疗和未治疗的感染小鼠中，胶质细胞增生和PrPres沉积是相似的。与未治疗的小鼠相比，他汀类药物治疗的小鼠由于晚期临床症状而接受安乐死的时间没有改变，这一发现与之前的报告不一致。我们的研究表明，测试的三种他汀类药物都不能有效地减少瘙痒病引起的神经炎症或神经发病。 在2017财年，我们在脑和脊髓以外的器官中检测了疾病诱导的PrPSc的病理和超微结构，在该模型中，无锚定的PrP以淀粉样聚集体的形式沉积在各种组织中。免疫金标记法鉴定的淀粉样蛋白PrPSc纤维在高倍镜下可见心脏、棕色脂肪、白色脂肪、结肠和淋巴组织的间质区域和血管周围。在棕色脂肪细胞和心肌细胞中，PrPSc淀粉样蛋白位于脂肪细胞的质膜上和质膜外，并似乎内陷和破坏这些类型的细胞的质膜，提示细胞损伤。相反，与淋巴组织和结肠中的巨噬细胞、结肠中的肠神经节细胞或白色脂肪中的脂肪细胞相关的PrPSc附近没有明显的细胞损伤。PrPSc定位于巨噬细胞吞噬酶体，缺乏可识别的纤维，可能正在降解。此外，与表达GPI锚定PrP的野生型小鼠相比，在TG锚定的小鼠的淋巴组织中，PrPSc与滤泡树突状细胞(FDC)没有关联，FDC也没有表现出典型的Prion相关的致病变化。因此，淀粉样蛋白PrPSc似乎在表达无锚定PrP的小鼠的PrP感染过程中对某些类型的细胞诱导了特异性损伤。

Prion diseases or transmissible spongiform encephalopathies are infectious neurodegenerative diseases of humans and animals. A major feature of prion diseases is the refolding and aggregation of a normal host protein, prion protein (PrP), into a disease-associated protease-resistant form (PrPres) which may contribute to brain damage. We previously documented the molecular details of the neuroinflammatory response in brain following scrapie infection. In FY17 we treated scrapie-infected mice with statin drugs to attempt to reduce neuroinflammation and prolong survival. In previous studies treatment of scrapie-infected mice with the Type 1 statins, simvastatin or pravastatin, showed a small beneficial effect on survival time. In the current study, to increase the effectiveness of statin therapy, we treated infected mice with atorvastatin, a Type 2 statin that has improved pharmacokinetics over many Type 1 stains. Treatments with either simvastatin or pravastatin were tested for comparison. We evaluated scrapie-infected mice for PrPres accumulation, gliosis, neuroinflammation, and time until advanced clinical disease requiring euthanasia. All three statin treatments reduced total serum cholesterol 40% in mice. However, gliosis and PrPres deposition were similar in statin-treated and untreated infected mice. Time to euthanasia due to advanced clinical signs was not changed in statin-treated mice relative to untreated mice, a finding at odds with previous reports. Our studies indicate that none of the three statins tested was effective in reducing scrapie-induced neuroinflammation or neuropathogenesis. In FY17 we examined the pathology and ultrastructure of disease-induced PrPSc in organs outside the brain and spinal cord in a model where anchorless PrP is deposited as amyloid aggregates in various tissues. Amyloid PrPSc fibrils identified by immunogold-labeling were visible at high magnification in interstitial regions and around blood vessels of heart, brown fat, white fat, colon, and lymphoid tissues. PrPSc amyloid was located on and outside the plasma membranes of adipocytes in brown fat and cardiomyocytes, and appeared to invaginate and disrupt the plasma membranes of these cell types, suggesting cellular damage. In contrast, no cellular damage was apparent near PrPSc associated with macrophages in lymphoid tissues and colon, with enteric neuronal ganglion cells in colon or with adipocytes in white fat. PrPSc localized in macrophage phagolysosomes lacked discernable fibrils and might be undergoing degradation. Furthermore, in contrast to wild-type mice expressing GPI-anchored PrP, in lymphoid tissues of tg anchorless mice, PrPSc was not associated with follicular dendritic cells (FDC), and FDC did not display typical prion-associated pathogenic changes. Thus, amyloid PrPSc appeared to induce specific damage to certain cell types during prion infection of mice expressing anchorless PrP.