在過去的一系列實驗研究中，紫草素(shikonin)，是由紫草(Lithospermum erythrorhizon)所萃取出來的主要成分，已被證實具有許多不同之細胞學及分生學之生物活性及藥理活性，例如傷口癒合、抗發炎及抗腫瘤等之活性等。此篇研究之主要目的為研判紫草素是否及如何涉及血管通透性之調節。在本文中，我們利用純化之紫草素塗抹於不同部位的小鼠皮膚上，包括耳朵、腹部及腿部之皮膚，而後分別於不同時間點手術取下處理過之皮膚標本，測試並探討在其調節血管通透性扮演重要角色之matrix metalloproteinases-2和-9(MMP-2和-9)以及E-cadherin之表現量。並且藉由Evans blue dye自血管滲入組織間的現象觀察血管通透性之情況。實驗結果顯示紫草素能夠提升小鼠皮膚中Evans blue dye的滲出量，以及經由紫草素塗抹之皮膚組織的MMP-9 and MMP-2酵素表現量也比控制組的量高出許多。此外，紫草素還能夠局部控制皮膚之血管通透性。在組織切片中，我觀察到小鼠皮膚的皮下層(subcutaneous layer)之厚度明顯增加。為了進一步探討紫草素在小鼠皮膚之組織是否會促進發炎反應，我們評估了與發炎反應相關之細胞激素interleukin-1β (IL-1β)及interleukin-6 (IL-6)之表現量，令人驚訝的是，經由紫草素塗抹之皮膚組織也可偵測到高量的IL-1β及IL-6。綜合以上所述，紫草素能夠有效增加皮膚之血管通透性及同時促進類似輕度發炎之反應，因此在改善藥物輸送效率及專一性的臨床應用上，我們認為紫草素具有作為不同皮膚敷劑藥物佐劑之潛力。Various previous studies have shown that shikonin, which is derived from medicinal plant Lithospermum erythrorhizon, can display diverse pharmacological beneficial effects or strong and specific bioactivities, e.g., in wound healing-, anti-inflammatory- and anti-tumor bioactivities. The aim of my present experimental study is to address whether and how shikonin may be involved in the regulation of vascular permeability in mouse skin tissues. Shikonin-treated skin samples originating from different organs, including ear, abdominal and leg skin of test mice, were collected at different time points tested, and protein expression levels of matrix metalloproteinases (MMP) and E-cadherin determined. Activity of vascular permeability was investigated by measuring the level of extravasation of Evans blue dye from blood vessels by Miles assay; also determined by the expression levels of MMP-2, MMP-9 and E-cadherin. MMP-2 and MMP-9 are two representative members of the MMPs family that play a critical role in regulation of vascular permeability. As revealed by Miles assay, shikonin exhibited high activity in extravasation of Evans blue dye from blood vessels to the adjacent dermal tissues, clearly indicating its leakage. Shikonin-treated skins samples showed higher protein expression levels for MMP-9 and MMP-2 when compared with vehicle control samples. To further evaluate whether shikonin can confer pro-inflammatory effect on skin tissue, the expression level of IL-1β and IL-6 were determined. High levels of IL-1β and IL-6 were found in shikonin-treated skins. Together, our data indicate that topical application of shikonin can effectively enhance vascular permeability in test skin, suggesting that shikonin may be clinically applicable as a potential adjuvant for use on improving the efficiency and specificity of drug delivery into adjacent tissues.
