鴉片類止痛藥物耐受性的轉譯研究: 從臨床到基礎

Abstract

鴉片類藥物是臨床處理中重度疼痛，最有效也最被廣泛使用的藥物。然而長期使用鴉片類藥物止痛卻也會伴隨產生藥物的耐受性。脊椎管內鴉片類藥物投與將藥物直接送至中樞神經產生藥效，是非常有效的止痛方式但卻也更容易產生藥物耐受性。傳統神經科學以神經元為中心的思維下，鴉片類藥物耐受性的致病機轉著重於Opioid receptor的internalization、NMDA receptor的upregulation或glutamate transporter 的down regulation。然而這些現象都只能部分解釋耐受性的成因。最近在齧齒類實驗動物上的研究結果顯示神經膠細胞的活化及發炎性物質的過度表現、也就是所謂的神經炎性反應在神經病變疼痛與類鴉片耐受性的致病機轉上有重要的角色。然而相關的人體研究證據則相當稀少。 在本研究的臨床部分，我們首先嘗試建立國內最完整的，有關體外可程控式植入型脊椎內給藥系統的照護流程。包括合適病患的選取、脊椎內嗎啡藥物輸注測試、手術方式的改進、長期追蹤與品質提升計畫。我們紀錄並分析了流程建立初期的病患，其脊椎管內嗎啡的劑量的改變、治療相關併發症的發生率與後續處理及病患日常生活功能的改善程度。藉由給予足夠劑量的脊椎管內嗎啡，病患的疼痛控制與生活品質皆能大幅改善。然而在這當中我們也發現所有接受脊椎內嗎啡輸注療法的病患，其嗎啡的劑量皆快速的增加，遠遠超過病情的演進。 以臨床的照護觀察到的現象為起點，在研究倫理委員會核准後，我們進行了一系列的轉譯醫學研究。我們首先分析了已產生類鴉片藥物耐受性病患的腦脊髓液中發炎相關因子的濃度。包括TNF-alpha、 CXCL1、CXCL10、CCL2、CX3CL1及CXCL12並與未暴露類鴉片藥物的對照組受試者比較。研究結果發現，已經對類鴉片止痛藥產生耐受性的病患群，其腦脊髓液中的CXCL1及CXCL12濃度明顯高於未暴露類鴉片藥物的對照組。進一步我們更發現CXCL1的濃度與病患所接受的類鴉片止痛藥物劑量成高度正相關。 接著我們建立轉譯動物實驗模式，藉由實驗鼠的閃尾反應，評估嗎啡的止痛效果及相關發炎因子對類鴉片耐受性產生的影響。在實驗大鼠投予嗎啡誘發藥物耐受性後，大鼠脊髓組織之CXCL1 及CXCL12 mRNA皆顯著增加。雖然單獨給予椎管內CXCL1或CXCL12並不會改變老鼠的基礎閃尾行為，然而椎管內給予CXCL1或CXCL12卻會大幅降低腹腔內給予嗎啡所造成的急性止痛效果。接著我們參照臨床長期椎管內類鴉片輸注用於頑固疼痛的處置，建立植入皮下微幫浦進行長期椎管內嗎啡輸注並誘發大鼠產生藥物耐受性的實驗模式。我們發現耐受性的發生會因同時給予嗎啡與CXCL1或CXCL12 而加速。反之 若被嗎啡輸注時一併給予CXCL1或CXCL12的中和抗體則會延緩耐受性的發生。針對CXCL1 訊息傳遞給予其受體CXCR2的拮抗劑antileukinate hexapeptide，或針對CXCL12 訊息傳遞給予其受體CXCR4的拮抗劑 AMD3100，則可更有效的延緩嗎啡耐受性的發生。 綜合以上的實驗結果，我們藉由臨床到實驗動物的轉譯醫學研究模式驗證了趨化激素CXCL1與CXCL12可能參與鴉片類止痛藥耐受性的形成。阻斷 CXCL1/CXCR2 與 CXCL12/CXCR4 的訊息傳遞路徑則可以延緩藥物耐受性的產生並降低其嚴重度。因此針對CXCL1/CXCR2 與 CXCL12/CXCR4 的訊息傳遞路徑進行介入將是治療類鴉片止痛藥耐受性的新藥研發之潛力標的。

Opioid analgesics remain the most effective and widely used analgesics for the management of moderate to severe pain. However, the efficacy of long-term opioid analgesics is progressively attenuated by tolerance, preventing adequate pain relief under stable opioid dosages for chronic pain patients. Although intrathecal opioid delivery provides very effective analgesia by acting directly on central nervous system, opioid analgesic tolerance is also accelerated. Classical neuron-centered concepts such as internalization of opioid receptors, up-regulation of N-methyl-D-aspartate receptor function, or down-regulation of glutamate transporter activity can only partially explain the phenomenon of tolerance. Recent evidence showing glial activation and upregulated inflammatory mediators in the rodent central nervous system has confirmed the pivotal role of neuroinflammation in neuropathic pain or opioid tolerance, or both. However, human evidence is still sparse. In clinical part of this study, we developed comprehensive management protocol for totally implantable programmable intrathecal drug delivery system from patient selection, intraspinal morphine trial, surgical procedure to follow up program. Intrathecal morphine dosage adjustment, treatment related complications and patient functional outcomes are recorded regularly and analyzed. By delivering liberal dose of intrathecal morphine, pain severity decreased significantly. Due to much better pain control and improved quality of life, functional performance status also improved. Intrathecal morphine delivery by using totally implantable programmable device is an effective alternative method to relieve refractory cancer pain. Based on our clinical practice, we further conducted subsequent translational research by investigating the intraspinal cytokine and chemokine profiles of opioid-tolerant cancer patients after research ethic committee approval. Cerebrospinal fluid (CSF) samples from opioid-tolerant cancer patients and opioid-naive subjects were compared. The CSF levels of tumor necrosis factor-alpha, CXCL1, CXCL10, CCL2, CX3CL1 and CXCL12 were assayed. CXCL1 and CXCL12 levels in CSF were significantly upregulated in the opioid-tolerant group. Further analysis revealed that CXCL1 level was strongly positively correlated with opioid dosage. The rat tail flick test was utilized to assess the effects of intrathecal CXCL1 or CXCL12 on morphine-induced acute antinociception and analgesic tolerance. After induction of tolerance by intrathecal morphine infusion, the spinal cord CXCL1 and CXCL12 messenger RNA were significantly upregulated. Although CXCL1 or CXCL12 infusion alone did not affect baseline tail flick latency, the analgesic tolerance was accelerated by intrathecal infusion of CXCL1 or CXCL12 in daily intraperitoneal morphine injection of paradigm. After establishing tolerance by intrathecal continuous infusion of morphine, its development was accelerated by co-administration of CXCL1 or CXCL12. On the contrary, tolerance was attenuated by co-administration of CXCL1 or CXCL12 neutralizing antibody or corresponding receptor antagonists. CXCL1 and CXCL12 were upregulated in both opioid-tolerant patients and rodents. The onset and extent of opioid tolerance was affected by antagonizing intrathecal CXCL1/CXCR2 and CXCL12/CXCR4 signaling. Therefore, the CXCL1/CXCR2 and CXCL12/CXCR4 signal pathways may be novel drug targets for the treatment of opioid tolerance.