NF-kB抑制劑可有效減鍰內毒素剌激之大白鼠腎臟內第二型正電荷胺基酸運輸酶之表現

NF-KB Inhibitors Significantly Attenuate the Transcription of High Affinity Type-2 Cationic Amino Acid Transporter in LPS-stimulated Rat Kidney

背景：過去文獻顯示敗血症所引起之腎臟衰竭與iNOS之誘導及大量一氧化氮（NO）合成有極密 切之關係；而第二型正電荷胺基酸運輪酶（包括CAT-2、CAT-2A、及CAT-2B）所調控L-arginine之 運輸更被證實是調控iNOS活性及NO合成之重要因素。吾人在一利用內毒素刺激以誘發敗血 症之大白鼠研究中發現敗血症會誘導腎臟CAT-2及CAT-2B之表現，而腎臟CAT-2A之表現則不 受影響。為進一步探討NF-KB之角色，吾人於是進行了以下以內毒素刺激導致敗血症之動物 實驗，來探討是否NF-kB在敗血症誘發之腎臟CAT-2及CAT-2B的表現上扮演重要之調控角色。方法：大白鼠隨機接受生理食盤水、內毒素、或內毒素合併NF-KB抑制劑（PDTC、dexametha-sone >或salicyltae）之注射，吾人於注射後第六小時分別犧牲大白鼠，收集之急速冷凍檢體則 加以檢驗分析以測量組織中iNOS，CAT-2，CAT-2A，及CAT-2B之滾度；並進一步測量分析腎臟內NO之合成及腎臟功能。結果：吾人發現大白鼠的腎臟之iNOS，CAT-2，及CAT-2B會被內毒素所誘發；而NF-KB抑制 劑可有放減緩內毒素刺激之大白鼠腎臟內iNOS，CAT-2，及CAT-2B之表現，進而經由抑制腎臟內之NO合成而有效減緩內毒素所致之腎臟傷害。而CAT-2A之表現則不受內毒素或NF-KB 抑制劑之影響。結論：內毒素會共同誘發腎臟iNOS，CAT-2，及CAT-2B之表現，而抑制NF-KB可有效減緩內毒 素之作用，進而抑制腎臟內NO之合成，有效減緩內毒素所致之腎臟傷害。

Background: Sepsis-induced renal failure is closely related to inducible nitric oxide synthase (iNOS) upre- gulation and nitric oxide (NO) overproduction. Trans-membrane L-arginine transportation mediated by type-2 cationic amino acid transporter (CAT-2) isozymes, including CAT-2, CAT-2A, and CAT-2B, is one of the crucial mechanisms that regulate NO biosynthesis by iNOS. We previously had shown that endotoxemia significantly upregulated renal CAT-2 and CAT-2B but not CAT-2A expression. This study was, thus, conducted to further explore the role of nuclear factor-KB (NF-KB) in regulating the expression of CAT-2 isozymes in lipopolysaccha- ride (LPS)-treated rat kidney. Methods: Adult male Sprague-Dawley rats were randomly given intra-peritoneal injections of normal saline (N/S), LPS, LPS plus NF-kB inhibitor pre-treatment (PDTC, dexamethasone, or salicylate), or an NF-kB inhibi-tor alone. The rats were sacrificed at 6 hours after LPS injection and enzyme expression and renal injury were examined. Results: Renal iNOS, CAT-2, and CAT-2B were significantly upregulated in LPS-stimulated rat kidney. NF-k B inhibitors significantly attenuated this upregulation induced by LPS and resultantly attenuated renal NO bio-synthesis and renal injury induced by LPS. In contrast, renal CAT-2A expression was not affected by either LPS or NF-kB inhibitors. Conclusions: LPS co-induces iNOS, CAT-2 and CAT-2B expression in LPS-stimulated rat kidney. Further-more, inhibition of NF-kB significantly attenuates NO biosynthesis through inhibition of iNOS, CAT-2, and CAT-2B, and, in turn, significantly reduces endotoxemia-induced renal injury.