由台灣漆中萃取出的漆酚之化學預防與抗癌功效研究

Abstract

10’(Z),13’(E),15’(E)-heptadecatrienylhydroquinone (HQ173)是由台灣漆(Rhus succedanea)純化出來漆酚中的一種。在本實驗室之前的研究發現，HQ173在高劑量濃度可以抑制數種癌細胞株生長，而造成細胞走向凋亡的途徑。在本實驗中，我們發現低劑量的HQ173並不會造成PBMC的細胞毒性，並且，若先以氧化物BSO傷害細胞，HQ173可以增加遭受BSO傷害的細胞存活率，於是我們推測HQ173具有引發化學預防的機制，保護細胞免於氧化傷害。結果發現，以10nM HQ173處理PBMC之後，細胞內SH在30分鐘後會降低13%，一小時後開始上升，而在兩小時後達到原本的含量，並且發現10nM HQ173刺激兩小時後可造成細胞內Nrf2進入細胞核中，造成細胞內NQO1 mRNA與GST 酵素活性增加。此外，分析上游磷酸酶發現MAPK可受到HQ173刺激而活化。我們認為當細胞受到10 nM HQ173刺激首先會使p38磷酸化而造成Nrf2活化進入細胞核中，接著便會影響下游phase 2 enzyme的表現。但值得一提的是這些現象都無法在HL-60血癌細胞中發現，故我們認為低劑量的HQ173是可以保護正常細胞，卻無法保護癌細胞。另外，在動物實驗中結果顯示，HQ173在F-344大鼠體內可以抑制肝癌細胞的生長，對於動物本身的生長卻沒有影響。在動物血清生化檢查數據觀察發現，經由腹腔注射HQ173對於動物的肝功能與腎功能都不造成影響。我們假設HQ173 在動物體內可以引發發炎反應而造成癌細胞凋亡，進而抑制癌細胞生長。在本實驗中可證明HQ173具有兩種功效，第一，低劑量的HQ173可以引發化學防禦機制而達到保護細胞免於氧化物的傷害，尤其是在保護正常細胞方面。其次，在動物實驗中我們發現HQ173可以抑制肝腫瘤的生長。綜合以上結果顯示，HQ173值得發展為化學預防的保健藥物或是癌症治療的藥物。

A novel urushiol, 10’(Z),13’(E),15,(E) -Heptadecatrienylhydroquinone (HQ173) purified from sap of the lacquer trees, Rhus succedanea, was found to inhibit several tumor cell lines growth and induced cell apoptosis. In the present study, we found HQ173 at low dosage (less than 1 uM) did not have cytotoxity in PBMC, and could overcome the oxidative toxicity of DL-Buthionine- [S,R]-sulfoximine (BSO). Results of this study in PBMC indicated that cellular sulfhydryl (SH) was depleted 13% at 30 min after HQ173-treatment and returned to original level after 2 hr. HQ173 could induce Nrf2 nuclear translocation at 2 hr after treatment. More nuclear Nrf2 were detected after 4 hr. NQO1 mRNA level and GST enzyme activity were induced by HQ173. Three major mitogen-activated protein kinases (MAPK) were activated after HQ173-treatment. We supposed that the p38 phosphorylation was induced by HQ173, which caused Nrf2 translocation to influence the downstream genes expression. On the other hand, those phenomenons were not found in HL-60 cells. The in vivo experiment was also observed. We found HQ173 could inhibit tumor growth in F-344 rats, and did not affect the growth of rats. The data of clinical chemistry showed there were no hepatoxicity and renal toxicity by intraperitoneal (ip) administration of HQ173. We hypothesized that HQ173 could induce immune response to cause tumor cell apoptosis, and proceed to the next step to cause inhibition of tumor growth in vivo. This study would verify that HQ173 had dual effects. First, HQ173 at low dosage could induce chemoprevention to protect cells against oxidants in PBMC. We considered the chemoprevention effect of HQ173 could protect normal cells, but not tumor cells. Second, HQ173 could inhibit hepatoma growth in vivo. To sum up, HQ173 would be worth to develop for chemoprevention and cancer therapy.