Interleukine-10 (IL-10)是一種親多功能的間白素(pleiotropic cytokine)，在免疫調節上具有重要的功能。IL-20又稱Zcyto10，屬於IL-10 family的一員，IL-10 family包含 IL-10、IL-19、IL-20、IL-22、MDA-7 (IL-24)以及AK155 (IL-26)。IL-20位於染色體1q32上，具有5個exon及4個intron，其胺基酸序列與其它IL-10 family的成員有24%~ 40%的相似性。現今已知IL-20過量表現的基因轉殖老鼠其皮膚的角質細胞有異常增生和分化的現象，顯示出類似於人類的牛皮癬（Psoriasis）病徵。由於目前對IL-20 in vitro的功能瞭解並不多，因此，本實驗室即在探討IL-20 promoter對基因的調控及其in vitro生物功能。
為瞭解IL-20的基因調控，我們經由5’ RACE定出轉錄起始點（transcription start site；TSS）所在，並由TSS往5’ 端挑選出八個不同長度：pA、pB、pC、pD、pE、pF、pG、pH（63bp~1950bp）的片段，分別構築在含有luciferase基因的質體上並進行transfection至HEK293及Madin-Darby canine kidney (MDCK) epithelial-like cells中表現。藉由luciferase的活性分析，發現pE（長度279 bp）可以驅使luciferase有最高的表現量。GM-CSF以及IL-10兩者皆可正向調控IL-20 promoter的活性，也能增加單核球(monocyte)中IL-20的轉錄本（transcripts）。此外，我們分析198位個體，發現有9%的健康個體以及9% SLE病人其IL-20 promoter 有318 bp insertion / deletion polymorphism。亦經由luciferase的活性分析，發現包含此318 bp-insertion的片段其promoter活性較不含這318 bp-insertion的片段活性低37%~72%，顯示出這318 bp-insertion可能具有調控基因的重要功能。
在IL-20 基因的組織分佈（tissue distribution）方面，我們找出人類在腎臟、肺臟與胎盤中會表現IL-20，小鼠IL-20則在大腦及心臟中會表現。此外，也發現人類及小鼠的IL-20因alternative splicing而有wild type（5個exon及4個intron）及short form（4個exon及3個intron）的表現，人類IL-20 short form 較wild type缺少exon 4；小鼠IL-20 short form則缺少exon 2。我們以E. coli系統來表達與純化小鼠IL-20 wild type和short form蛋白質，並進一步分析此兩種蛋白質in vitro的生物功能。結果發現這兩種蛋白質皆會刺激單核球產生IL-6與TNF-α。此外，IL-20 wild type較short form能刺激CD8+ T細胞產生較多量的ROS （reactive oxygen species）。另外，經由Quantitative Real-Time PCR分析，發現小鼠IL-20 wild type及short form也會促進CD8+ T 細胞產生KGF-1（keratinocyte growth factor-1）、TNF-α及IL-6。由上述的結果發現，我們推測IL-20在發炎反應中有其重要性，並可能刺激CD8+ T細胞產生KGF-1而作用於角質細胞（keratinocyte），導致角質細胞不正常的增生、分化與產生牛皮癬的病徵。

IL-10 is a pleiotropic cytokine with important functions in immunoregulation. IL-20 (also called zcyto10) belongs to the IL-10 family, which includes IL-10, IL-19, IL-20, IL-22, MDA-7 (IL-24), and AK155 (IL-26). IL-20 locates on chromosome 1q32. It consists of five exons and four introns. The polypeptide sequence of IL-20 shares homology with other IL-10 family members. It had been shown that IL-20 transgenic mice showed phenotype similar to human psoriasis, demonstrating abnormal keratinocytes proliferation and differentiation. Little is known about the in vitro biological function of IL-20. Therefore, we aimed to study the in vitro biological function and gene regulation of IL-20. To understand the gene regulation of human IL-20, we identified the human IL-20 transcription start site by 5’ RACE, isolated the promoter sequence, and analyzed its promoter activities. Eight fusion genes containing different regions upstream of exon 1 (63 bp-1950 bp) linked to a luciferase reporter gene were expressed in HEK293 and Madin-Darby canine kidney (MDCK) epithelial-like cells. Some fusion genes showed luciferase activity higher than that of the positive control, the SV40 promoter fusion gene. We identified a fusion gene (pE) containing 279 bp upstream of exon 1 that showed promoter activity 14-fold greater than that of the negative control. Both GM-CSF and IL-10 showed up-regulation of the promoter activity of IL-20 and induced IL-20 transcripts in monocytes. Analysis of IL-20 promoter from 198 individuals, both healthy individuals and patients with SLE, showed that there is a 318 bp insertion-deletion polymorphism on the IL-20 promoter. Insertion of this 380 bp in the promoter region decreased its promoter activity by 37% to 72%. It indicated that the 318 bp insertion could impact on gene regulation. In tissue distribution of IL-20, we found human IL-20 was expressed in kidney, lung, placenta, while mouse IL-20 was expressed in brain and heart. We also isolated two alternatively spliced transcripts from human and mouse cDNA libraries. Exon 4 was deleted in the human short form of IL-20, while exon 2 was deleted in the mouse short form of IL-20. In order to investigate the IL-20 biological function, we have purified mouse recombinant IL-20 wild type and short form protein expressed in E. coli system. We demonstrated that both IL-20 wild type and short form protein induced production of IL-6 and TNF-a in monocytes; up-regulated the transcripts of keratinocyte growth factor-1 (KGF-1), IL-6, and TNF-a in CD8-positive T cells; and induced the production of reactive oxygen species (ROS) from CD8-positive T cells. These results suggest that IL-20 play an important role in inflammatory reaction and the involvement of IL-20 in psoriasis may be mediated through targeting CD8-positive T cells.

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