近來，IL-10已被指出可以透過抑制免疫反應與抑制血管內皮細胞的血管新生使得動脈粥狀硬化的區域減少(Pinderski Oslund, et al.,1999)。此外，IL-10家族成員之一IL-24也被指出可以抑制內皮細胞的分化(Differentiation)與移行作用(Migration)等血管新生作用而抑制腫瘤生長(Ramesh, et al.,2003)。文獻中也指出，血管的內皮細胞層有IL-20R1與IL-20R2的表現(Blumberg, et al.,2001)，這也表示血管內皮細胞也是IL-10家族細胞激素的作用目標細胞之一。因此我們推論血管內皮細胞也是這些新穎細胞素的作用目標之一。而同屬於IL-10家族成員的IL-20，先前的研究指出他與角質細胞增生的致病機轉息息相關，至於IL-20對於內皮細胞的作用尚未被清楚的了解，因此我們先利用CPAE (小牛犢肺動脈內皮細胞) 以及HUVEC (人類臍靜脈內皮細胞) 進行in vitro 的細胞實驗。實驗結果指出，IL-20會促進內皮細胞的增生(Poliferation)，而這個現象可以被IL-20的單株抗體以及sIL-20R1 (soluble IL-20 receptor 1)，sIL-20R2所抑制。此外，由我們實驗室所發現的IL-20的Alternatively-spliced variant，稱之為IL-20 short form (IL-20S)，同樣也可以促進內皮細胞的增生。當內皮細胞同時處理IL-10以及IL-20時，IL-10可以減弱IL-20促使內皮細胞增生的現象。而IL-20同時也可以促使內皮細胞的移行(Migration)以及分化(Differentiation)，並且促使bFGF，VEGF，MMP-2，以及 MMP-9 (僅有IL-20S) 的transcripts表現量增加。此外，我們也探討IL-20作用在內皮細胞時所引發的訊息傳遞路徑，不論是IL-20W或是IL-20S皆會引發ERK1/2，p38，以及JNK這三條訊息傳遞路徑的磷酸化。另一方面，我們也發現當內皮細胞處於缺氧的情況下，IL-20以及他的受器(receptors)其transcripts表現量皆有增加的現象。此外，IL-20亦可促進內皮細胞中IL-6以及IL-8的表現。因此，我們推論IL-20是一個多功能型的細胞激素並且是一個新穎的血管新生因子。

　IL-20 belongs to the IL-10 family and is involved in the pathogenesis of keratinocyte proliferation in vivo. To determine whether IL-20 acts on target cells other than keratinocytes, we treated human umbilical vein endothelial cells (HUVECs) and calf pulmonary artery endothelial cells (CPAEs) with human IL-20 and analyzed its effect on endothelial cells. We demonstrated that IL-20 induced proliferation of endothelial cells in a dose dependent manner. Anti-human-IL-20 monoclonal antibody and soluble (s)IL-20 receptor (R)1 and sIL-20R2 blocked IL-20-induced proliferation. We also isolated an alternatively-spliced transcript of IL-20 from human cDNA libraries. Exon 4 was deleted in the human short-form of IL-20. The alternatively-spliced variant also induced proliferation of HUVECs and CPAEs. When IL-10 and IL-20 were co-incubated with HUVECs, IL-10 diminished IL-20-induced proliferation of HUVECs and CPAEs. IL-20 also significantly induced HUVEC migration and tube formation on matrigel. Incubation of IL-20 with HUVECs and CPAEs also induced transcripts of bFGF, VEGF, MMP-2, and MMP-9 (IL-20S only). Both IL-20W and IL-20S induced ERK1/2, p38, and JNK phosphorylation in HUVECs. Upregulation of IL-20 and its receptors were mediated through hypoxia. Furthermore, incubation of HUVECs with IL-20 up-regulated IL-6 and IL-8 production. Thus, IL-20 is a pleiotropic cytokine and a novel angiogenesis factor.

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