第二型前列腺素還原酶在實驗性敗血症中的角色:功能與機制之探討

Role of prostaglandin reductase 2 in experimental sepsis: functional and mechanistic studies

陳膺中(Ing-Jung Chen)

指導教授 ： 莊立民

國立臺灣大學/醫學院/分子醫學研究所/博士(2016年)

https://doi.org/10.6342/NTU201603357

摘要

敗血症(Sepsis)是一種系統性的發炎反應，伴隨因感染引起的多重器官失去功能。各種不同的前列腺素的功能在敗血症中均受到廣泛的研究，尤其前列腺素和其代謝產物在先天免疫系統和免疫反應調節中均扮演重要角色。15-keto-PGE2是前列腺素E2 下游的代謝產物，且為過氧化物酶體增殖物活化受體 (PPARγ) 的內源性受體，經由前列腺素還原酶-2 (PTGR2)代謝。 此外，我們已知15-keto-PGE2在脂肪細胞分化過程中作為PPARγ活性調節者，同時對CTFR-/-老鼠模式中疾病的進展至關重要。然而至今，我們對15-keto-PGE2 及其代謝酵素PTGR2在發炎反應中所扮演的角色仍然未知。
在本篇論文中，我們提供了對15-keto-PGE2以及其代謝酵素PTGR2在活化巨噬細胞方面功能性和機制層面的探討。首先，內毒素所誘發的巨噬細胞中會產生大量15-keto-PGE2。此外，減少PTGR2表現會導致15-keto-PGE2的累積，造成巨噬細胞無法正常活化並減少細胞激素分泌。當我們加入外源性15-keto-PGE2或PTGR2 knockdown的細胞均顯現出抗氧化反應序列(ARE)的報告基因活性與其下游抗氧化基因表現上升。我們更進一步發現，和正常細胞相較，PTGR2 knockdown 細胞中表現較低濃度的活性氧類(ROS)，和較大量的抗氧化基因表現。就機制層面而言，外源性15-keto-PGE2會促進細胞中NRF2累積和高分子量的Keap1合成。最後我們發現，不論是PTGR2基因剔除鼠或15-keto-PGE2治療組的小鼠, 均能提高實驗性敗血症的存活率。總括而言，我們確認15-keto-PGE2為內源性的抗氧化促進者，亦提供了15-keto-PGE2和PTGR2缺失造成的免疫抑制效應的實驗證據，證明了PTGR2與15-keto-PGE2在發炎反應進程中的重要性，也為未來PTGR2 和15-keto-PGE2作為抗發炎標靶開啟了新的可能性。

關鍵字

前列腺素還原酶-2 ； 15-keto-PGE2 ； NRF2 ； 抗發炎反應 ； 活性氧類 ； 敗血症

並列摘要

Sepsis is a systemic inflammation accompanied by multi-organ dysfunction due to infection. Distinct prostaglandin metabolism has been widely studied in this condition and many of these prostaglandins and their metabolites play important role in the regulation of innate immune response. 15keto-PGE2 is a prostaglandin E2 metabolite catalyzed via prostaglandin reductase 2 (PTGR2). It was previously characterized as an endogenous ligand for peroxisome proliferator-activated receptor gamma (PPARγ) and played important regulatory roles in adipocyte differentiation and disease progression in CTFR-/- animals. However, little is known about the role of 15keto-PGE2 and the catabolic enzyme PTGR2 during the development of inflammation.
In this thesis, we present functional and mechanistic analyses of 15keto-PGE2 and PTGR2 in macrophages activation. LPS-induced macrophages resulted in a substantial upregulation of 15keto-PGE2 level. Furthermore, disruption of PTGR2 showed significant accumulation of 15keto-PGE2 and resulted in impaired macrophages activation and cytokines suppression. Exogenous treatment of 15keto-PGE2 and PTGR2 knockdown cells exhibited augmented antioxidant response element (ARE) reporter activity, along with the upregulation of antioxidant genes expressions. Mechanistically, 15keto-PGE2 promoted NRF2 accumulation independently of PPARγ activity. Furthermore, PTGR2 knockdown cells presented lower basal ROS level and higher antioxidant response genes expressions compared to control cells. Lastly, ptgr2-deficient mice were more resistant to endotoxin or cecal ligation and puncture (CLP)-induced sepsis. Taken together, we identified 15keto-PGE2 as an endogenous activator of antioxidant response and provided evidence of the immune-suppressive effect of 15keto-PGE2 and PTGR2 deficiency via in vitro and in vivo experiments. Our study affirms the significance of PTGR2 and 15keto-PGE2 in the progression of inflammatory response and suggest a novel anti-inflammatory therapy through targeting PTGR2/15keto-PGE2.

並列關鍵字

PTGR2 ； 15-keto-PGE2 ； NRF2 ； Anti-oxidant ； ROS ； Sepsis

參考文獻

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