利用自體免疫腦脊髓炎小鼠模式探討奈米物質於神經發炎的影響

Abstract

奈米科技被定義為「於奈米尺度的限制下，所發展出具有獨特性及可改善性能之技術」。在中樞神經疾病的診斷中，超順磁性奈米鐵具有多樣的檢測應用能力及治療潛力，舉例來說，奈米鐵的藥物製劑可作為核磁共振成像的顯影劑，協助評估血腦障壁破損面積及偵測多發性硬化症病患的神經發炎病灶位置。隨著其臨床應用廣泛，奈米鐵對神經免疫系統會造成的免疫毒性影響也日漸被關注。然而，奈米鐵對於中樞神經系統的報告大多都在探討其於正常健康小鼠或是細胞實驗中的毒性影響。因此，本研究利用模擬多發性硬化症之病程及其免疫機制的自體免疫腦脊髓炎小鼠模式，試著探討奈米鐵在神經發炎情況下所造成的潛在影響。結果顯示，以靜脈注射方式給予小鼠奈米鐵的後3天，其鐵離子可在腦及脊髓中被偵測到，並且，單劑量奈米鐵的給予顯著地加劇小鼠之臨床症狀、神經去髓鞘化及發炎細胞的浸潤現象，還伴隨著微膠細胞的活化及輔助性第一型T細胞的增生。此些結果證實，全身性奈米鐵的暴露可能會藉由促進微膠細胞及輔助第一型T細胞的活化，進而加劇自體免疫腦脊髓炎小鼠的症狀嚴重度。 多發性硬化症仍持續在尋求一個有效、便利及無毒性的治療方式，和朴酚已被證實具有抗發炎及神經保護的能力，然而，和朴酚的不溶於水特質及無法以靜脈注射方式給予的不便利性，大幅阻礙其臨床應用價值。因此，本研究嘗試以奈米微脂體當作藥物載體，探討以靜脈注射方式給予奈米化和朴酚對於自體免疫腦脊髓炎小鼠的治療效果。結果顯示奈米化和朴酚減緩其疾病嚴重度，並且降低神經去髓鞘化和發炎細胞的浸潤，同時也抑制活化的微膠細胞及輔助性第一型T細胞浸潤至腦脊髓炎小鼠的脊髓中。由結果得知，奈米化和朴酚可藉由調控微膠細胞及輔助性第一型T細胞的活化進一步減緩腦脊髓炎所造成的症狀。 總結以上，本論文旨在探討奈米鐵及奈米化和朴酚於神經發炎情況下的影響。有鑑於免疫毒性研究結果指出，奈米鐵對於自體免疫腦脊髓炎的促神經發炎作用，可能會對多發性硬化症病患的神經免疫系統帶來潛在的免疫毒性隱憂。並且，經由免疫藥理研究證實，此奈米化和朴酚劑型有望成為未來治療多發性硬化症的一個前瞻性策略。

Nanotechnology is defined as the development of strategy with special and improved properties under nanoscale confinement. Superparamagnetic iron oxide nanoparticles (IONP) possessed various diagnostic and promising therapeutic applications in the treatment of central nervous system (CNS) diseases. For example, IONP have been extensively utilized as contrast agents for magnetic resonance imaging (MRI) to assess the integrity of blood-brain barrier and monitor the inflammation status in patients with multiple sclerosis (MS). With the increasing application, the immunotoxic impact of IONP exposure on the neuroimmune homeostasis of the CNS had been concerned. However, most of the studies primarily addressed the effects of IONP on cell cultures or healthy animals. Hence, in the study, we tried to explore the potential impact of IONP on neuroinflammation in a murine model of experimental autoimmune encephalomyelitis (EAE), which mimics many characteristic inflammatory features of MS. Results showed that iron content were examined in both the brain and spinal cord of EAE mice 3 days after intravenous injection of IONP. A single dose of IONP aggravated the clinical symptoms, accompanied by marked demyelination and the infiltration of inflammatory cells. Furthermore, IONP treatment increased the activation of microglia and the number of T helper (Th) 1 cells in the spinal cords of EAE mice. These results demonstrated that systemic exposure to IONP might augment the disease severity of EAE by promoting the activation of microglia and Th1 cells. On the other side, there is ongoing research looking for more effective, convenient, no toxicity treatments for MS. Honokiol (HNK) has been found to exhibit stronger anti-inflammatory and neuroprotective effects. However, the application of honokiol is limited due to its poor water solubility and viability for intravenous administration. Hence, nanosomes as delivery vehicles were developed for the intravenous injection of HNK to study its therapeutic efficacy on EAE. NHNK ameliorated the clinical symptoms accompanied by the decreased demyelination and inflammatory cell infiltration. Moreover, the number of activated microglia and Th1 cells in the spinal cords of EAE mice was reduced by NHNK treatment. These results indicate that NHNK reduced the infiltration of activated microglia and Th1 cells into spinal cords, and caused the improvement of the severity of EAE. In summary, the present study demonstrated the impacts of nanomaterials, including IONP and NHNK, on the murine model of EAE. The immunotoxic study points out that the pro-inflammatory effects of IONP on neuroinflammation associated with EAE implicates as a potential risk of IONP exposure on neuroimmunity in patients with MS. The immunopharmaceutical study points out that the formulation of NHNK is a promising therapeutic strategy for inflammatory CNS diseases, such as MS.