我的研究目的是利用剔除「血栓烷A2合成酶/血栓烷A2/血栓烷前列腺素受體」(TXAS / TXA2 / TP)的基因，來阻斷它的信號傳導，檢驗是否可以減少小鼠的腎臟缺血/再灌注的損傷。「血栓烷A2合成酶/血栓烷A2/血栓烷前列腺素受體」(TXAS / TXA2 / TP)的正常生理功能，可促進血管收縮，以及血小板凝集，幫助人體在受傷時止血。但在許多病理情況下，會造成「血栓烷A2合成酶/血栓烷A2/血栓烷前列腺素受體」(TXAS / TXA2 / TP)過度活化，誘發氧化傷害，例如，心肌梗塞，肺高壓，子癲前症，器官移植，狼瘡腎炎，敗血性休克，腎絲球腎炎，以及各類血栓疾病。在以上的病理情況下，血栓烷A2合成酶（TXAS）活性會增強，刺激血栓烷A2（TXA2）釋放和血栓烷前列腺素受體（TP）活化，造成嚴重的血管收縮和氧化損傷。因此，本研究利用基因剔除「血栓烷A2合成酶/血栓烷A2/血栓烷前列腺素受體」(TXAS / TXA2 / TP)的訊號傳遞，期待瞭解更多關於腎臟缺血/再灌注損傷的病理機轉，並希望能在這樣的基礎上研究出治療方法。中醫藥有數千年的傳承，其中，活血化瘀藥的使用，在中醫治療腎臟病中，扮演重要的角色，但其中的現代藥理機轉，仍有待進一步研究。活血化瘀的效果，類似現代生理的血管擴張與抗凝血作用，與TXA2的效果相反。因此，本研究希望這次的實驗結果，可以在未來作為研究中醫活血化瘀藥物治療腎臟病的研究模型，以期揭開中醫神秘的面紗，並找出中醫藥在現代疾病的應用。
本研究分別在以下四種基因型小鼠TXAS+/+TP+/+，TXAS–/–,TP–/–以及TXAS–/–TP–/–身上，評估了靜脈注射U46619（TXA2模擬物）和45分鐘腎缺血再灌注（I/R）所造成的的腎臟血流動力學變化和腎損傷。我檢驗了腎臟中TXAS和TP的基因表達狀況，血尿素氮（BUN）和肌酐酸，活性氧（ROS）的量，還有促炎性細胞因子和細胞死亡的病理生理機轉，包括I/R損傷下造成的的細胞凋亡，細胞自噬和細胞焦亡。
實驗結果發現，在野生型的小鼠(TXAS+/+TP+/+)身上，腎臟的缺血/再灌流(I/R)，增強了TXAS，TP的表現；也增強了發炎及氧化壓力相關的參數，包括細胞核中NF-κB，NADPH氧化酶gp91的表現；三種計畫性細胞死亡的參數，也有顯著增加，包括細胞凋亡(Bax / Bcl-2 / Caspase-3)，細胞自噬(Beclin-1 / LC3 II)，細胞焦亡Caspase-1 / gasdermin D / IL-1β)。而且，野生型小鼠中腎臟TXB2濃度，ROS含量，血中尿素氮，肌酐酸，在經過缺血/再灌流(I/R)之後，都有顯著上升。而能夠 擴張血管的eNOS在腎臟中的表達下降。
在另外三種基因剔除小鼠中(TXAS–/–,TP–/–以及TXAS–/–TP–/–)，所有的增強參數均顯著降低。在TXAS+/+TP+/+和TXAS–/–小鼠中，靜脈注射U46619顯著抑制了腎微循環並增強了gp91和Bax / Bcl-2；在TP–/–和TXAS–/–TP–/–，靜脈注射U46619，則沒有這種效果。腎臟的缺血再灌流，顯著降低了四組小鼠的腎臟微循環，但是跟野生型小鼠(TXAS+/+TP+/+)相比，TXAS–/–, TP–/– 和TXAS–/–TP–/–這三組小鼠，恢復至基準線腎血流量的時間顯著縮短。由以上可知，阻斷(TXAS / TXA2 / TP)信號傳導，可減弱I/R造成的促炎細胞因子增加。
由本研究的結果可知，透過基因剔除來阻斷TXAS / TXA2 / TP信號傳導，可透過抗氧化，抗發炎，抗凋亡，抗自噬和抗焦亡的作用，對於缺血/再灌流造成的腎損傷產生保護作用。TXAS / TXA2 / TP信號傳遞路徑，主要的正常生理作用為促進血小板凝結，跟促進血管收縮。中醫的活血化瘀藥，常用於治療腎臟病。而這些活血化瘀中藥的效果，類似現代藥理作用中，促進血流增加與抗凝血的作用，與TXA2的作用相反。因此，在未來，我們可以利用本研究的動物模型來測試，中醫活血化瘀藥物治療腎臟病的機轉，是否與抑制TXAS / TXA2 / TP信號傳遞路徑有關。

Aims: Enhancement of thromboxane A2 (TXA2) synthase (TXAS) activity, TXA2 release and thromboxane-prostanoid (TP) receptor activation leads to vasoconstriction and oxidative injury. We explored whether genetic deletion of TXAS/TXA2/TP signalling may reduce renal ischaemia/reperfusion (I/R) injury in mice.

Methods: Renal haemodynamics and function were evaluated in TXAS+/+TP+/+ (wild type, WT), TXAS–/– (TXS–/–), TP–/– and TXAS–/–TP–/– (double knockout, dKO) mice in response to intravenous TXA2 mimetic-U46619 and 45-min renal ischaemia and 4-h reperfusion injury. We examined renal TXAS and TP expression, blood urea nitrogen (BUN) and creatinine, reactive oxygen species (ROS) amount, pro-inflammatory cytokines and pathophysiologic mechanisms, including apoptosis, autophagy and pyroptosis under I/R injury.

Results: Renal I/R enhanced the levels of TXAS, TP, nuclear factor-κB, NADPH oxidase gp91, Bax/Bcl-2/caspase-3/apoptosis, Beclin-1/LC3-II/autophagy, caspase-1/gasdermin D/interleukin-1β/pyroptosis, renal thromboxane B2 (TXB2) concentration, ROS amount, plasma BUN, creatinine and TXB2 and decreased renal endothelial nitric oxide synthase expression in WT mice. All these enhanced parameters were significantly decreased in three knockout mice. Intravenous U46619 significantly decreased renal microcirculation and enhanced gp91 and Bax/Bcl-2 in WT and TXS–/– but not TP–/– and dKO mice. I/R significantly decreased renal microcirculation in all mice; however, the time for recovery to baseline renal blood flow level was significantly shortened in TXS–/–, TP–/–and dKO mice versus WT mice. Blockade of TXAS/TP signalling attenuated I/R-enhanced pro-inflammatory cytokine profile.

Conclusion: Blockade of TXAS/TXA2/TP signalling confers renal protection against I/R injury through the actions of anti-oxidation, anti-inflammation, anti-apoptosis, anti-autophagy and anti-pyroptosis.

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