HMGB1在化療藥物引起神經痛之角色

Abstract

化療引起周邊性神經病變(chemotherapy-induced peripheral neuropathy, CIPN)為常見且具有劑量依賴性的副作用，症狀包含麻木、刺痛感，影響患者的生活品質，而需要調整劑量或換藥，進而造成治療效果改變。造成CIPN的明確機轉尚不清楚，其中一部份可能的原因為發炎性細胞激素(inflammatory cytokines)的釋放導致神經發炎。 許多文獻指出高遷移率族蛋白1 (high mobility group box 1 protein, HMGB1)於化療引起神經痛中可能扮演重要的角色，HMGB1為廣泛表現於哺乳類動物細胞的核蛋白，當細胞死亡或受損時便會被動的釋放；在細胞外環境，HMGB1為多功能蛋白質，可誘導發炎前驅細胞激素(proinflammatory cytokines)，導致不正常的發炎反應。另外，動物研究顯示類鐸受體(toll-like receptors 4, TLR4)過度表現與神經痛高度相關，而神經細胞上的TLR4為HMGB1的受體。因此本論文欲探討HMGB1/TLR4途徑是否參與化療藥物造成的神經痛。結果顯示臨床上治療大腸癌的化療藥物組合益樂鉑(oxaliplatin)以及fluorouracil(5-FU)會使大腸癌細胞株HCT116與WiDr的HMGB1基因表現上升並釋放HMGB1。含有HMGB1的癌細胞上清液會使神經細胞株SH-SY5Y上的TLR4增加，加入HMGB1抑制劑glycyrrhizin或aspirin可逆轉TLR4的過度表現。利瑞卡(pregabalin)可降低大腸癌細胞HMGB1基因表現與細胞外HMGB1濃度，pregabalin加上含有HMGB1的癌細胞上清液也能減少神經細胞SH-SY5Y上的TLR4。此外，千憂解(duloxetine)為目前唯一於大型臨床試驗證明有效減緩神經痛的藥物，研究結果顯示duloxetine不影響癌細胞外HMGB1的濃度，但能直接作用在神經細胞SH-SY5Y，減少TLR4的表現，且當duloxetine加上含有HMGB1的癌細胞上清液則能大幅降低SH-SY5Y上TLR4的表現，暗示duloxetine治療神經痛的機轉可能有一部份是透過影響HMGB1/TLR4途徑。經由本研究，未來能以此機制為基礎發展出類似藥物以減少病人產生化療引起神經痛的不良反應。

Chemotherapy-induced peripheral neuropathy(CIPN) is a debilitating adverse effect. It may result from abnormal functioning of peripheral or central nervous system and is characterized by paresthesia, dysesthesia, and deficits in normal sensation, which reduces quality of life and the efficacy of treatment. However, the molecular mechanisms underlying the chemotherapy-induced neurotoxicity and dysfunction are still not entirely understood. Accumulating evidence supports that neuropathic pain is associated with neuroinflammation. Recent study implicates that HMGB1 is involved in the induction and maintenance of CIPN. HMGB1 is a non-histone DNA-binding protein which is engaged in many physiological activities. Extracellular HMGB1 is known as a pro-inflammatory mediator which plays a pronociceptive role in animal models. Moreover, emerging evidence indicate that toll-like receptor 4 (TLR4) which recognizes HMGB1 is highly expressed and strongly correlated with development of behavioral hypersensitivity in CIPN models. Therefore, we investigated whether oxaliplatin/5-FU treatment affect HMGB1/TLR4 pathway. Real-time PCR confirmed that oxaliplatin/5-FU induced HMGB1 mRNA upregulation in colon cancer cell lines WiDr and HCT116 and extracellular HMGB1 concentration was increased, which subsequently led to TLR4 overexpression in neuroblastoma cell line SH-SY5Y. Glycyrrhizin and aspirin which have been proven to be HMGB1 inhibitors could reverse TLR4 upregulation. Pregabalin which is an optional treatment of neuropathic pain suppressed oxaliplatin/5-FU-induced HMGB1 overexpression and extracellular HMGB1 concentration in a dose-dependent manner. Pregabalin also suppressed HMGB1-induced TLR4 upregulation in SH-SY5Y. Duloxetine, used for treatment of chronic pain, had no effect on HMGB1 release from colon cancer cells whereas duloxetine directly attenuated the expression of TLR4 in SH-SY5Y cells as well as HMGB1-induced TLR4 overexpression, suggesting that the therapeutic mechanism may be in part through HMGB1/TLR4 inhibition. Future studies are warranted for verifying the detailed mechanisms as well as developing therapeutic strategies for prevention of CIPN.