Yamaoka Masakazu, Shimizu Hiroko, Takahashi Toru, Omori Emiko, Morimatsu Hiroshi
Department of Anesthesiology and Resuscitology, Okayama University Medical School, Okayama, Japan.
Department of Faculty of Health and Welfare Science, Okayama Prefectural University, Okayama, Japan.
PLoS One. 2017 Jul 13;12(7):e0180934. doi: 10.1371/journal.pone.0180934. eCollection 2017.
Free heme, a pro-oxidant released from myoglobin, is thought to contribute to the pathogenesis of rhabdomyolysis-associated acute kidney injury (RM-AKI), because renal overexpression of heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, confers protection against RM-AKI. BTB and CNC homology 1 (Bach1) is a heme-responsive transcription factor that represses HO-1. Here, we examined the changes with time in the gene expression of Bach1, HO-1, and δ-aminolevulinate synthase (ALAS1, a heme biosynthetic enzyme) in the rat kidney using an RM-AKI model induced by the injection of 50% glycerol (10 mL/kg body weight) into bilateral limbs. We also examined the protein expression of Bach1 in the nucleus and cytosol, and HO-1 in the rat kidney. Glycerol treatment induced significant elevation of serum creatinine kinase and aspartate aminotransferase levels followed by the marked elevation of serum blood urea nitrogen and creatinine levels, which caused serious damage to renal tubules. Following glycerol treatment, HO-1 mRNA and protein levels were significantly up-regulated, while ALAS1 mRNA expression was down-regulated, suggesting an increase in the free renal heme concentration. The Bach1 mRNA level was drastically increased 3 h after glycerol treatment, and the increased level was maintained for 12 h. Nuclear Bach1 protein levels were significantly decreased 3 h after treatment. Conversely, cytosolic Bach1 protein levels abruptly increased after 6 h. In conclusion, we demonstrate the dynamic changes in Bach1 expression in a rat model of RM-AKI. Our findings suggest that the increase in Bach1 mRNA and cytosolic Bach1 protein expression may reflect de novo Bach1 protein synthesis to compensate for the depletion of nuclear Bach1 protein caused by the induction of HO-1 by free heme.
游离血红素是肌红蛋白释放的一种促氧化剂，被认为与横纹肌溶解相关的急性肾损伤（RM-AKI）的发病机制有关，因为血红素加氧酶-1（HO-1，血红素分解代谢的限速酶）在肾脏中的过表达可对RM-AKI起到保护作用。BTB和CNC同源蛋白1（Bach1）是一种血红素反应性转录因子，可抑制HO-1。在此，我们使用向双侧肢体注射50%甘油（10 mL/kg体重）诱导的RM-AKI模型，研究了大鼠肾脏中Bach1、HO-1和δ-氨基乙酰丙酸合成酶（ALAS1，一种血红素生物合成酶）基因表达随时间的变化。我们还检测了大鼠肾脏中细胞核和细胞质中Bach1的蛋白表达以及HO-1的蛋白表达。甘油处理导致血清肌酸激酶和天冬氨酸转氨酶水平显著升高，随后血清尿素氮和肌酐水平显著升高，这对肾小管造成了严重损伤。甘油处理后，HO-1的mRNA和蛋白水平显著上调，而ALAS1的mRNA表达下调，提示肾脏游离血红素浓度增加。甘油处理后3小时，Bach1的mRNA水平急剧升高，且升高水平持续12小时。处理后3小时，细胞核Bach1蛋白水平显著降低。相反，细胞质Bach1蛋白水平在6小时后突然升高。总之，我们证明了RM-AKI大鼠模型中Bach1表达的动态变化。我们的研究结果表明，Bach1 mRNA和细胞质Bach1蛋白表达的增加可能反映了Bach1蛋白的从头合成，以补偿游离血红素诱导HO-1导致的细胞核Bach1蛋白的消耗。
