中草藥對LPS活化NF-kB抑制機轉之研究

Abstract

轉錄因子NF-kB在免疫發炎反應、細胞的增生、分化與癌化等生理反應中扮演了關鍵性的角色，且也與許多疾病的發生有相關性。NF-kB平時會與其調控蛋白IkB結合，而形成一個不活化的複合體存在細胞質中，當受到外來的刺激，IkB會降解而使得NF-kB會進入細胞核，進而活化下游基因的轉錄（transcription）。 在此研究中，我們利用實驗室中先前完成的，能穩定持有可檢驗NF-kB活化與否的蟲螢光酵素報導基因的小鼠巨噬細胞株（RAW264.7），來篩檢中草藥內可以調控免疫發炎反應的有效成分。在篩檢一系列的中草藥初萃層後，發現編號19-3的中草藥初萃層能有效的抑制內毒素（LPS）活化NF-kB的作用。 為了進一步的了解此現象的分子調控機轉，設計了一系列的實驗做研究。初步發現，中草藥初萃層19-3抑制內毒素活化NF-kB，不是經由降解NF-kB的調控蛋白IkB所造成。進一步實驗發現，中草藥初萃層19-3可能經由直接或間接的去調控NF-kB的活化，其會影響細胞內NF-kB的分部情形。綜合以上，在此研究中，我們篩檢了一系列的中草藥後僅發現初萃層19-3能抑制LPS活化NF-kB，而在分子機轉方面，還需由進一步的實驗加以探討。

NF-kB is an important transcription factor regulating numerous genes involved in immune and inflammatory responses, cell growth, cell survival, apoptosis, and tissue differentiation. It is also suggested to be involved in the pathogenic progression of many diseases. In resting cells, NF-kB is maintained in an inactive form in the cytoplasm through interaction with inhibitory protein, IkBs. Upon receipt of an appropriate signal, NF-kB is release from IkB and translocate to the nucleus, activate target gene transcription. In this project, we utilized a RAW (p4XNFkB-Lucneo) stable clone generated in our laboratory to screen for the bioactive components in Chinese herbs that were documented to exhibit anti-inflammatory activity. We found that the Chinese herb extract 19-3 could significantly reduce LPS-induced NF-κB activation. The molecular mechanism of Chinese herb extract 19-3 was also partially elucidated by Western blot analysis. Preliminary result shows that 19-3 inhibits LPS-induced NF-kB activation is not involved in suppressing IkBa degradation. Further studies shows that 19-3 may mediate the transactivation of NF-kB directly or indirectly. The subcellular distribution of NF-kB was also affected by the treatment of 19-3. In conclusion, we screened several Chinese herbs and found at least one fraction from Chinese herb 19-3 exhibited a suppressive activity to LPS-induced NF-kB activity. The molecular mechanism of 19-3 needs to be further elucidated.