抑鈣素基因相關胜肽在偏頭痛之角色︰年齡差異、診斷及治療

Abstract

背景 青少年偏頭痛無論在臨床症狀和藥物的反應都有別於成人，其原因尚不清楚。三叉神經血管系統（TGVS）及其分泌的降鈣素基因相關胜肽（CGRP）被認為是偏頭痛形成的重要因素之一。本論文即研究經枕骨大孔注入辣椒素（capsaicin）誘發TGVS神經發炎(neurogenic inflammation)反應，比較幼鼠和成鼠的差別，及其對抗偏頭痛藥物的不同反應。臨床研究方面則探討血漿CGRP在兒童偏頭痛之診斷與治療上應用的價值。另外，已知CGRP也可自心臟之特定組織分泌，而部分心房中膈缺損（ASD）患者經導管修復缺損後併發偏頭痛，因此進一步研究血漿CGRP在此病症所扮演的角色。 方法 TGVS反應包含檢視三叉神經和頸神經（TCC）之c-Fos表現、三叉神經節和硬腦膜之CGRP表現及硬腦膜之蛋白質外漏程度。同時建立公式，以距obex +0.6、-1.2、 -9 mm 以及+0.6、-0.6、-6 mm之c-Fos表現的神經元數分別估計成鼠和幼鼠之TCC表現的總量。採辣椒素刺激前給藥方式，檢視此動物模式對valproic acid 或 topiramate之反應。血漿CGRP以ELISA方式檢測，而偏頭痛失能指標則以PedMIDAS問卷評估。檢體則於發作時或發作間以及進行ASD手術前取得。另外，為研究抗偏頭痛藥物之療效，亦記錄服用急性治療藥物及至少服用預防性藥物二週後的反應。 結果 經辣椒素刺激，幼鼠與成鼠之TCC活化神經元數目無明顯差異，但幼鼠之周邊反應較不明顯，包含三叉神經節之CGRP表現、硬腦膜之CGRP之釋出和硬腦膜之蛋白質外漏不明顯。藥物反應方面，幼鼠之TCC活化神經元明顯被valproic acid (100 mg/kg, p=0.011) 及 topiramate (30 mg/kg, p=0.002; 100 mg/kg, p=0.006)抑制，而成鼠方面之抑制反應則較不明顯。臨床研究方面，前瞻性收集121位受試者的134 個檢體，其中66位為偏頭痛患者，33位非偏頭痛之頭痛患者，及22位非頭痛患者，年齡4-18歲。發現偏頭痛患者之CGRP值較非偏頭痛者高(p=0.007)，又偏頭痛組中，發作時之CGRP值高於發作間值(p=0.036)，然而在非偏頭痛組則未見此差異。此現象亦在同一受試者接受兩次抽血，比較其發作和發作間之CGRP值獲得證實(n=9; p=0.015 vs. n=4; p=0.47)。若以發作時CGRP值55.1 pg/ml為閥值，則預測偏頭痛之敏感度為0.81，而專一度為0.75。高CGRP值者(>200 pg/ml, n=7)之偏頭痛失能指數較低CGRP值者(<200 pg/ml, n=33)有偏高的趨勢(26.7 vs. 19.32, p=0.16)。進一步檢視CGRP值是否可預測患者服藥之反應，前瞻性收集68位5-18歲偏頭痛患者，發現62人(91%)需急性藥物和47人(69%)需預防性藥物治療。Naproxen即使為第二線藥物，其療效仍優於第一線的acetaminophen (減少頭痛50%以上有效率：56 vs. 42%)，而預防藥物方面，第一線之topiramate 優於 flunarizine (70 vs. 55%)，且二者之副作用發生率相同(10%)。需急性治療組之血漿CGRP值(284.4±47.2 pg/ml, n=62)與不需者無明顯差異(347.7±223.6 pg/ml, n=6; p>0.05)；然而，需預防治療組之血漿CGRP值(364.1±61.8 pg/ml, n=47)則高於不需者(183±54.3 pg/ml, n=21; p=0.031)。又服用topiramate有效者之CGRP值(437.2±131.1 pg/ml, n=14)高於無效者 (66.8±19.4 pg/ml, n=6; p=0.015)，而此現象則未見於其他預防性藥物。另外，為探討ASD修復後新生偏頭痛之形成原因，收集40位術前未曾頭痛發作之患者做分析。17名連續患者於術前接受CGRP檢測，其中4 名(23.5%)術後有偏頭痛發作。又發現ASD缺損較大者(20±0.9 vs. 16±1 mm, p= 0.009)及術前CGRP值較低者 (21.1±3.9 vs. 90.1±27.1 pg/mL, p= 0.042)易有術後新生偏頭痛。有5人接受兩次以上檢測，其頭痛發作時之CGRP值高於發作間值(257.2±45.5 vs. 45.6±25.5 pg/mL, p= 0.03)。 結論 基礎研究方面，本動物模式之年齡差異反應與臨床上之觀察雷同，即幼鼠對刺激較成鼠不敏感。而幼鼠對valproic acid或topiramate之抑制反應則較成鼠明顯。臨床研究方面，血漿CGRP值應用於兒童偏頭痛之診斷、生活失能及治療方面，具有正面價值。而ASD缺損大小及術前低CGRP值為預測術後新生偏頭痛之潛在指標。且與一般偏頭動患者相同，發作時之血漿CGRP值皆高於發作間值，暗示CGRP敏感度可能為致病的原因之一。以上研究結果有助於吾人了解偏頭痛之病理、診斷、及治療，並開拓新視野，同時也有助於未來開發兒童偏頭痛之新藥。

Background: Pediatric migraine displays different clinical features and drug response from adult migraine. The etiology of migraine remains unclear but the trigemino-vascular system (TGVS) is believed to play an important role. In a rat model of migraine induced by intra-cisternal (i.c.) instillation of capsaicin, we compared TGVS responses in adolescent and adult rats and their responsiveness to clinically effective antimigraine drugs, such as valproic acid and topiramate. Calcitonin gene-related peptide (CGRP), shown to be released from TGVS and also from specific cardiac tissues, can be measured in human plasma samples. Clinically, we also investigated the role of plasma CGRP in the diagnosis and pharmacological treatment of pediatric migraine and also in new-onset migraine headache attacks (MHAs) after transcatheter closure of atrial septal defect (ASD). Methods: In animal studies, both central and peripheral TGVS responses were measured. The central response was measured by the number of c-Fos-protein-expressing neurons in the trigeminal cervical complex (TCC). Peripheral responses measured included CGRP expression in the trigeminal ganglia (TG) and dura mater, and dural protein extravasation. The formulae for estimating total numbers of activated TCC neurons were established based on the c-Fos-positive neuronal numbers in three sample sections, +0.6, -1.2 and -9 mm and +0.6, -0.6 and -6 mm, from the obex in adult and adolescent rats, respectively. Pretreated drug responsiveness to valproic acid and topiramate were examined. In clinical studies, plasma CGRP concentrations were measured by enzyme-linked immunosorbent assay and migraine disability by the pediatric migraine disability assessment (PedMIDAS) questionnaire. Blood sampling for CGRP measurement in children with migraine and non-migraine headache during or between headache attacks, and in age and gender matched control subjects as well as patients with ASD before or after transcatheter closure of ASD (ASO). In the study investigating the outcome of pharmacological therapy for pediatric migraine, in addition to plasma CGRP levels, we also recorded the responses to both acute and preventive therapies in which the patients took each preventive drug for at least 2 weeks. Results: After capsaicin instillation, adolescent rats had comparable numbers of activated TCC neurons as adult rats, but less TGVS peripheral responsiveness than adults, including CGRP immunoreactivity in the TG, and protein extravasation and CGRP depletion (inversely reflected by CGRP immunoreactivity) in the dura mater. In adult rats, total numbers of c-Fos reactive neurons after capsaicin stimulation are not significantly inhibited by valproic acid and topiramate, whereas, in the adolescent rats, they were significantly suppressed by valproic acid at 100 mg/kg (p=0.011) and topiramate at 30 (p=0.002) and 100 mg/kg (p=0.006). Clinically, we prospectively collected 134 blood samples during or between attacks from 66 migraine, 33 non-migraine headache (non-migraine) and 22 non-headache patients, aged 4-18 years. Migraineurs had higher plasma CGRP levels than non-migraine patients (p=0.007). The attack level was higher than the non-attack level in migraine (p=0.036), but not non-migraine, patients. This was also revealed in paired comparison (n=9; p=0.015 vs. n=4; p=0.47). Using a threshold of 55 pg/ml, the sensitivity of the attack level for predicting migraine was 0.81, and specificity 0.75. The PedMIDAS score tended to be higher in the high CGRP (>200 pg/ml, n=7) group than the low (<200 pg/ml, n=33) group (26.07 vs. 19.32, p=0.16), although not statistically significant using Mann-Whitney test. In the study investigating if the plasma CGRP level can predict pharmacological therapy outcome in pediatric migraineurs, we prospectively recruited 68 patients with migraines, aged 5-18 years. Sixty-two patients (91%) required acute therapy whereas 47 patients (69%) needed preventive treatments. Even as a second line therapy, naproxen was better than acetaminophen in terms of more responders with 50% headache reduction (56 vs. 42%). As for the first line preventive therapy, the response rate of topiramate was higher than flunarizine (70 vs. 55%) with comparable adverse effects (10%). Plasma CGRP levels were not significantly elevated in patients requiring acute therapy (284±47 pg/ml, n=62), compared to those who did not require (348±224 pg/ml, n=6; p>0.05), whereas they were higher in patients requiring preventive therapy (364±62 pg/ml, n=47) than those who did not require (183±54.3 pg/ml, n=21; p=0.031). The plasma CGRP levels of the responders to topiramate (437±131 pg/ml, n=14) were significantly higher than the non-responders (67±19 pg/ml, n=6; p=0.015), while there were no significant differences between responders and non-responders to the other drugs. For studying the role of CGRP in patients with new-onset MHAs after ASO, we prospectively collected patients before and after closure and measured plasma CGRP levels. Forty patients who had ASD but no previous migraine were enrolled. Four (23.5%) of the 17 consecutive patients whose CGRP levels were checked before ASO had new-onset MHAs. The patients with MHAs had a bigger ASD size (20±1 vs. 16±1 mm, p= 0.009) and lower CGRP levels before closure (21±4 vs. 90±27 pg/mL, p= 0.042) than those without. Among the 5 patients with blood samplings both during and between attacks, a paired comparison revealed a significantly increased level of CGRP during attack (257±46 vs. 46±26 pg/mL, p= 0.03). Conclusions: In a migraine animal model induced by i.c. capsaicin administration, we found less TGVS responsiveness and higher therapeutic responsiveness to either valproic acid or topiramate in adolescent rats than adults. This is reminiscent of less severe migraine and different pharmacological outcomes in pediatric patients clinically. In clinical studies, plasma CGRP levels are useful for the diagnosis and the prediction of disability and pharmacological treatment outcome in pediatric migraine. A bigger ASD size and lower plasma CGRP levels before ASO can be potential predictors of new-onset MHAs. Furthermore, a significant increase in CGRP levels during migraine attack implies that the occurrences of new-onset MHAs after ASO correlate with the release of CGRP. It suggests that CGRP sensitization from a lower baseline possibly involves in the occurrence of new-onset MHAs after ASO. All of these results may provide new insight into the pathophysiology, diagnosis and treatment of migraine and guide the development of new anti-migraine drugs for children.