マウス横紋筋融解症誘発性急性腎障害モデルにおけるNrf2活性化の意義の検討

生体は親電子性物質，活性酸素種によって生成される酸化ストレスから生体を保護する応答システムを有している．Keap1（Kelch-like ECH-associated protein 1） -Nrf2（NF-E2 related factor2）システムがこの応答機構において重要な役割を果たす．核内移行したNrf2は転写因子として，NQO1，HO-1などの抗酸化遺伝子群の発現を制御する．　横紋筋融解症による急性腎障害（AKI: Acute Kidney Injury）の機序として，酸化ストレスが尿細管障害に大きく関与する．それ故，横紋筋融解症誘発性AKI においてもNrf2活性化による腎保護効果が期待される．横紋筋融解症誘発性AKI におけるNrf2活性化の意義と治療標的としての可能性を検討した．ヒト近位尿細管上皮細胞（hPTECs）を用いhemin 刺激に対するNrf2活性化の意義を検討した．hemin 刺激によりhPTECs におけるNrf2関連抗酸化遺伝子群の上昇，細胞障害を認めた．Nrf2-siRNA によるNrf2ノックダウン（KD）を行うことでhemin 刺激に対する抗酸化遺伝子群の発現上昇は抑制され，細胞障害が有意に増悪した．野生型マウス （WT），Nrf2欠損マウス（Nrf2KO）を用い，グリセロール筋注による横紋筋融解症モデルを作成した．（１）WT/Cont，（２）WT/ 横紋筋融解症（RM），（３）Nrf2KO/Cont，（４）Nrf2KO/RM の４群で比較検討した．結果は，WT/Cont に比べWT/RM 群で腎機能障害，尿細管障害，マクロファージ浸潤を認め，Nrf2KO/RM 群で有意に増悪した．抗酸化遺伝子群の発現はNrf2KO/RM 群で低下していた．　横紋筋融解症誘発性AKI において，Nrf2活性化が腎保護効果を有する事が示された．横紋筋融解症によるAKI に対して，Nrf2活性化が新たな治療標的となり得ることが明らかとなった．Cells are equipped with cytoprotective systems against oxidative stress caused by reactive oxygen species and electrophilic stress. The Keap1-Nrf2 pathway plays a central role in such mechanisms against oxidative and xenobiotic damage. Nrf2, as a transcription factor, activates a series of genes including NQO1 and HO-1.As the mechanism of acute kidney injury (AKI) due to rhabdomyolysis, renal tubule injury due to oxidative stress is the major component of the pathology. Therefore, in rhabdomyolysisinduced AKI, reno-protective effect of Nrf2 activation is expected. In the present study, the role of Nrf2 activation in rhabdomyolysis-induced AKI was investigated. In vitro, human proximal tubular epithelial cells (hPTECs) were used to determine the significance of Nrf2 for hemin stimulation. Hemin stimulation revealed elevation of Nrf2-related antioxidant gene group and cytotoxicity. Nrf2 knockdown (KD) with Nrf2-siRNA suppressed the rise of the expression of the antioxidant genes against hemin stimulation, and the cell damage was significantly exacerbated. A model of rhabdomyolysis by glycerol intramuscular injection was also prepared in vivo using wild type mice (WT) and Nrf2-deficient mice (Nrf2 KO). These mice were of the C57BL/6J background. We divided them into four groups: (1) WT/Cont, (2) WT/rhabdomyolysis (RM), (3) Nrf2 KO/Cont, and (4) Nrf2 KO/RM. Renal dysfunction and macrophage infiltration occurred more often in the WT/RM than in the WT/Cont, and it significantly worsened in the Nrf2 KO/RM group compared to the WT/RM. The expression of the antioxidant gene group was suppressed more in the Nrf2 KO/RM group compared with the WT/RM.These results indicate that Nrf2 activation exerts reno-protective effect in rhabdomyolysisinduced AKI. Nrf2 activation may be a new therapeutic target for rhabdomyolysis-induced AKI

ミゾリビンによる急性尿酸性腎症とメソトレキサートによる骨髄抑制を併発した1例

症例は83歳,男性.近医で関節リウマチの診断で加療(プレドニゾロン2mg,メソトレキサート(MTX)4mg),他に高尿酸血症,高血圧で加療中であった.当院へ入院13日前にミゾリビン(MZ)150mg追加投与された.入院2日前に食欲不振と全身倦怠感で近医を受診,尿素窒素99.5mg/dl,クレアチニン7.8mg/dlと急性腎不全を認めたため当院へ紹介入院した.入院時の検査所見で尿酸26.5mg/dLと著明な高尿酸血症を認めMZによる急性尿酸性腎症と診断した.そのためMZ及び尿酸の除去を目的に緊急血液透析を施行した.尿酸値及び腎機能は速やかに改善した.しかし,入院後より血小板及び白血球数の減少を認めた.骨髄検査では骨髄異形成症候群様であり,MZに加えMTXの関与を推測された.その後汎血球減少も改善している.本症例はMZの血中濃度も高くMZの排泄遅延による高尿酸血症のため急性腎不全を合併し更に腎機能の増悪がMTXによる無効造血を発症した可能性が考えられた.MZと尿酸も血液透析により体外への除去が可能でありMZによる急性尿酸性腎症の場合は早急な血液透析が有効である.An 83-year-old man was diagnosed with rheumatoid arthritis at a nearby hospital for which he was administered methotrexate (MTX) and prednisolone. Thirteen days before admission, he had started mizoribine (MZ) 150mg. Two days before admission to our hospital, he was admitted to a nearby hospital for appetite loss and general fatigue. Laboratory tests showed renal dysfunction at nearby hospital, and he was consequently admitted to our hospital for further examination. On admission, we reasoned that renal dysfunction had resulted from hyperuricemia during MZ administration because the serum concentration of uric acid (26.5mg/dL) and MZ (trough level, 5.14μg/mL) were markedly elevated. Accordingly, MZ treatment was terminated, and hemodialysis was initiated. The patient subsequently showed an improvement in his condition and renal function recovered. However, pancytopenia developed soon after admission, and bone marrow aspiration showed myelodysplastic syndrome-like lesions. We suspected MTX and MZ to be the main cause of pancytopenia. Because the onset of acute renal failure had been attributed to MZ, it was conjectured that the dose of MTX was too high. Therefore, MTX administration was cancelled, and pancytopenia ameliorated. In cases of transient renal dysfunction with MZ, it is necessary to consider discontinuation of MZ and initiation of hemodialysis

Comparison of Left Ventricular Diastolic Function Parameters between Patients with Unplanned and Planned Hemodialysis Initiation: A Cross-Sectional Study

Despite the increasing number of dialysis patients, there is still no clear consensus regarding when a permanent access device should be prepared and renal replacement treatment should be undertaken. The purpose of this study was to evaluate left ventricular diastolic function at the start of dialysis between patients in a planned or unplanned manner according to the 2016 recommendations of the American Society of Echocardiography/European Association of Cardiovascular Imaging (ASE/EACVI). We designed a single-center, cross-sectional study to use echocardiography to evaluate and compare left ventricular diastolic function at the onset of dialysis between patients in planned and unplanned groups. A total of 21 patients were included in our analysis (11 initiated dialysis in a planned manner and 10 did so in an unplanned manner). E/A and E/E′ were significantly high in the unplanned dialysis initiation group (p = 0.048 and p = 0.003, respectively). Furthermore, the number of patients with an E/E′ ratio of >14 and tricuspid regurgitation velocity of >2.8 was also significantly high in the unplanned dialysis initiation group (80% vs. 18%; p = 0.009, 40% vs. 0%; p = 0.035, respectively). According to the American Society of Echocardiography and the European Association of Cardiovascular Imaging Recommendation in 2016, the number of patients with left ventricular diastolic dysfunction was significantly high in the unplanned dialysis initiation group (80% vs. 18%; p = 0.009). The current study demonstrated that left ventricular diastolic dysfunction is more apparent in incident dialysis patients in an unplanned manner. Our findings suggest that the assessment of left ventricular diastolic function by echocardiography may be an indication of when to create a permanent access device and initiate dialysis

C/EBP-β Modulates Transcription of Tubulointerstitial Nephritis Antigen in Obstructive Uropathy

Tubulointerstitial injury leading to fibrosis is a common pathway of many renal diseases. During this type of injury, modeled by unilateral ureteral obstruction (UUO), cells undergo epithelial-to-mesenchymal transition (EMT), a process that is mediated by various cytokines that modulate the biology of extracellular matrix proteins. Here, we studied the tubulointerstitial nephritis antigen (TINag), a tubular basement membrane protein, in the UUO model of tubulointerstitial injury. We observed upregulation of type IV collagen but downregulation of both laminin and TINag in obstructed kidneys. TINag downregulation was a result of oxidative stress; in the proximal tubular epithelial cell line HK-2, TINag expression and its promoter activity decreased after treatment with H2O2. We identified multiple CCAAT/enhancer binding protein β (C/EBP-β) motifs in the TINag promoter and observed that oxidant stress perturbed interactions between TINag DNA and C/EBP-β protein. Oxidant stress reduced nuclear translocation of C/EBP-β in HK-2 cells, which was restored by antioxidants. In addition, overexpression of C/EBP-β restored the H2O2-induced reduction of TINag promoter activity and expression. Furthermore, in vivo, renal obstruction reduced nuclear expression of C/EBP-β. Cells grown on a TINag substratum maintained their normal epithelial phenotype and cytoskeletal organization, similar to those grown on type IV collagen, and demonstrated reduced synthesis of fibronectin. Taken together, these findings suggest that altered interactions between C/EBP-β and TINag play a critical role in the pathophysiology of renal injury after obstruction