【作者】 韩梅；

【导师】 李英；

【作者基本信息】 河北医科大学 ， 内科学， 2012， 博士

【摘要】 急性肾损伤(acute kidney injury, AKI),既往被称为急性肾衰竭,是指肾功能突然下降,但病程在3个月以内的一组临床综合症。研究显示,在危重症病人中AKI的发病率可达30-50%,而由脓毒症引发的AKI(sepsis-induced AKI or septic AKI)约占AKI总发病率的50%。Septic AKI病人具有更紧急的入院情况、更多的合并症和更高的危险评分,而且即使我们治疗危重症的方法和支持手段在不断进步,septic AKI病人的死亡率仍然高达60%。Septic AKI病人的不良预后有着很多原因,首先是我们对septic AKI的病理生理机制尚不完全清楚,局限了我们对治疗方法的改进；此外在临床工作中,血清肌酐(serum creatine,SCr)仍然是诊断和治疗AKI的检测指标,但它会受到肌肉质量、血压和饮食中蛋白质摄入量等诸多因素的影响,且与肾脏细胞的急性损伤间无明确的相关性。因此SCr并不是能够及时而准确的反应AKI的生物学标志物,不能使我们在AKI的初期就能做出诊断并及时的逆转肾细胞的损伤,我们需要寻找新的AKI的生物学标志物。在目前已确认的AKI的生物学标志物中,中性粒细胞明胶酶相关脂质运载蛋白(neutrophil gelatinase-associated lipocalin,NGAL)被认为是最为重要和理想的标志物。众多研究在造影剂相关性肾病和缺血/再灌性AKI(心脏术后AKI和肾移植术后AKI)病人中对NGAL的临床诊断价值进行了评价。显示NGAL是AKI良好的诊断标志物,其敏感性为0.815。近几年来,也有几项研究评价了NGAL对儿科或成人危重病病人septic AKI的诊断和预测价值。然而,NGAL作为septic AKI诊断标志物时出现了一些难以解释的问题,无论血清中的NGAL (serum NGAL,sNGAL)还是血浆中的NGAL (plasma NGAL,pNGAL)虽然具有很高的诊断敏感性,但是诊断的特异性却很低。而尿液中的NGAL (urinary NGAL,uNGAL)显示了更好的诊断特异性,只在脓毒症合并AKI的病人中升高,在未合并AKI的病人中并不升高。体液中NGAL在诊断AKI时出现的不确定性,为诊断和治疗AKI带来了困扰。因此,我们应该进一步研究septic AKI时肾脏NGAL的变化规律及与s/pNGAL、uNGAL的关系,以能正确分析NGAL在临床检测AKI时表现出来的差异。目前,对于NGAL和肾组织内细胞损伤机制之间关系的研究还很有限,NGAL作为AKI的生物学标志物,是否能够及时反应肾组织细胞内损伤机制的变化还不明确。对于septic AKI、NGAL与肾组织内炎症反应的关系应是首要的研究课题。此外,NGAL作为肾脏上皮细胞在脓毒症时表达增多的一个急性期蛋白,它在受损上皮细胞中的作用尚不明确,也值得进一步探讨。基于以往的研究资料,本研究通过制备和观察内毒素(lipopolysaccharides，LPS)损伤所致的septic AKI大鼠模型,及应用LPS刺激的人肾近端小管上皮细胞系(HK-2),从在体水平及细胞水平明确NGAL mRNA的表达规律,并进一步观察了NGAL mRNA与pNGAL uNGAL、肿瘤坏死因子α(tumor necrosis factor,TNFα)、白介素-6(interleukin-6,IL-6)、细胞凋亡间的关系,为将NGAL更好的应用于临床septic AKI病人的诊断、治疗中提供了切实的理论依据。1内毒素致大鼠脓毒症性急性肾损伤模型的制备目的：采用适当剂量的LPS腹腔内注射致大鼠发生AKI,通过观察血肌酐水平和肾组织病理改变以明确肾损伤,为以后的实验研究提供科学而稳定的动物模型。方法：按照处理因素和时间的不同将大鼠分为6组,每组6只。对照组(Con)为盐水处理组,给予0.9%盐水(1m1)腹腔内注射；其余5组为LPS处理组,给予大鼠腹腔内注射LPS(3.5mg/kg),分别处理1、3、6、12、24h,并按照处理时间设定为：LPS1h组、LPS3h组、LPS6h组、LPS12h组、LPS24h组。实验各组按照预设时间点,采集血液标本以测定血肌酐水平,留取肾脏标本行光镜及电镜下病理组织学观察以明确肾损伤。结果：①SCr在LPS处理后3-12h升高,LPS3h、LPS6h、LPS12h组与Con组相比有显著差异(P<0.01)；②光镜下肾组织病理学检查可见损伤以肾皮质中的肾小管上皮细胞最为显著,表现为细胞水肿,官腔变小。细胞损伤以LPS处理后3-12h最为严重；透射电子显微镜观察到肾近端小管上皮细胞微绒毛紊乱、受损,细胞内水肿,线粒体外膜受损等损伤的表现,还可见核膜固缩、染色质边集的凋亡细胞。小结：大鼠腹腔内注射LPS可以诱导出现septic AKI,septic AKI发生时以肾小管上皮细胞的病理损伤为主,并可见细胞凋亡。这一动物模型为下一步观察肾损伤标志物-NGAL提供了实验基础。2脓毒症性急性肾损伤肾组织内NGAL的表达变化及意义目的:NGAL虽然能够作为septic AKI的较为理想的生物学标志物,但是肾损伤时肾组织内NGAL的表达变化与体液中NGAL水平及肾组织内炎症反应的关系尚不明确。此次研究目的是在前期制备的septic AKI大鼠模型的基础上,进一步明确NGAL mRNA在肾组织中的变化规律和表达部位,肾组织内NGAL mRNA与TNFαmRNA、IL-6mRNA的相关性及与sNGAL、uNGAL的关系。方法：动物分组和处理同第一部分。实验各组按照预设时间点采集标本。采集血液及尿液标本以ELESA方法测定NGAL水平,留取肾脏标本应用原位杂交技术确认NGAL mRNA的表达部位及表达强度,并应用qRT-PCR方法检测LPS处理后肾组织中NGAL mRNA与TNFα mRNA、IL-6mRNA的表达水平。结果：①应用原位杂交技术,发现Con组大鼠的肾脏中NGAL mRNA只在远曲小管上皮细胞和髓质的集合管细胞中有微弱的表达,近曲小管细胞完全不表达。而在LPS1h、LPS3h、LPS6h、LPS12h各组,即在LPS处理后1-12h, septic AKI大鼠肾组织中NGAL mRNA的表达明显增强,34.3%-49.6%的肾皮质内的小管上皮细胞为NGALmRNA+,并观察到肾近端小管上皮细胞也同时表达NGAL mRNA。在LPS处理后LPS24h组,大鼠的肾组织中NGAL mRNA的表达明显减弱。②肾组织中TNFαmRNA、IL-6mRNA的表达在LPS处理后即刻升高。TNFα mRNA在LPS1h组即达高峰,为Con组的24.18±6.39倍,与Con组相比差异显著(P<0.01),而后TNFα mRNA下降,在LPS处理3h后,各组TNFα mRNA与Con组相比无差异(P>0.05)；IL-6mRNA在1-3h显著升高,LPS1h、LPS3h组与Con组相比差异显著(P<0.01),其在LPS3h组达高峰,为Con组的68.40±11.04倍。IL-6mRNA在LPS处理6h后下降至正常水平,与Con组相比无显著差异(P>0.05)；NGALmRNA在LPSlh、LPS24h组与Con组比较无显著差别(P>0.05),但在LPS3h、LPS6h、LPS12h各组,即LPS处理后3-12h,表达显著上调,与Con组相比差异显著(P<0.01),其峰值水平出现在LPS6h组,为Con组的226.71±37.22倍；虽然NGAL mRNA在肾组织内表达上调和下降均滞后于炎性因子,但TNFα mRNA与NGAL mRNA之间显示了良好的相关性,(r=0.995,P<0.001),而IL-6mRNA与NGAL mRNA间不相关(r=0.276,P=0.653)。③pNGAL与uNGAL在LPS处理后即刻升高。pNGAL在1-24h均维持升高水平,LPS1h、LPS3h、LPS6h、LPS12h及LPS24h组与Con组相比均差异显著(P<0.01)；因LPS1h组大鼠无尿,uNGAL显示从LPS3h组显著升高,并在LPS3h、LPS6h、LPS12h各组,即LPS处理后3-12h,维持升高水平,与对照组相比差异显著(P<0.01),uNGAL在LPS24h组回降到Con组水平(P>0.05);pNGAL峰值水平为192.68±14.37ng/ml,出现在LPS3h组,而uNGAL峰值水平为154.42±12.75ng/ml,出现在LPS6h组；uNGAL水平与肾组织内NGAL mRNA水平密切相关(r=0.850,P<0.001)；但pNGAL水平与肾组织内NGAL mRNA水平无相关性(r=0.328,P>0.05)。小结：当septic AKI发生时,受损的肾小管上皮细胞显著上调表达NGAL mRNA,上调水平与肾组织内的核心炎症因子TNFα的上调水平密切相关；uNGAL水平与肾组织内NGAL mRNA的变化密切相关,真实的反映了肾损伤状态；而pNGAL水平与肾组织内NGAL mRNA的变化不相关,提示pNGAL并不是septic AKI的良好标志物。这一研究结果为能更好的应用NGAL诊断septic AKI提供了新的理论依据。3内毒素诱导肾小管HK-2细胞中NGAL的表达及抗凋亡机制的研究目的：在本课题的前期研究中,我们发现肾小管上皮细胞即是septicAKI时损伤的主要部位,也是NGAL的主要表达部位,而NGAL与细胞损伤机制间的确切关系尚不明确。因此,此次研究的目的是应用LPS刺激人肾脏近端小管上皮细胞(HK-2),观察NGAL mRNA和caspase3mRNA的表达变化及二者间的相关性。并应用siRNA沉默HK-2细胞中的NGAL基因,以观察NGAL对caspase3mRNA及细胞凋亡水平的影响,从而明确在septic AKI时,受损的肾脏上皮细胞中NGAL的保护作用及机制。方法：①将HK-2细胞以5×105个/ml的密度接种于6孔板内,常规培养24h后分为6组,为Con组和LPS处理组。LPS处理组分为5组,更换含有LPS50uM的单纯培养基,分别培养1、3、6、12、24h,并按照培养时间设定为：LPS1h组、LPS3h组、LPS6h组、LPS12h组、LPS24h组。以上各组到达预设时间点后,将细胞收集,以qRT-PCR方法检测NGAL mRNA、Caspase3mRNA的表达水平；②将HK-2细胞以2×105个/ml的密度接种于6孔板内,应用只含有10%胎牛血清,而无抗生素的培养基培养24h。而后将细胞孔板分为Con、LPS、siRNA3、siRNA3+LPS共4组。其中Con、LPS组只更换单纯培养基进行培养,而siRNA3、 siRNA3+LPS组加入含有转染试剂(NGAL siRNA3)的培养基,转染36h,并于荧光倒置显微镜下观察转染效果；而后Con和siRNA3组更换单纯的培养基,LPS和siRNA3+LPS组更换含有LPS50uM的培养基,继续培养3h。以上各组到达预设时间点后,将细胞收集,以qRT-PCR方法检测NGAL mRNA、Caspase3mRNA的表达水平；③按照方法②中的方式培养及处理HK-2细胞后,以流式细胞仪及TUNEL法检测各组HK-2细胞的凋亡情况。结果：①LPS50uM刺激HK-2细胞后,NGAL mRNA在LPS1h、 LPS3h、LPS6h组,即LPS处理后1-6h内显著升高(LPS1h组和LPS3h组,P<0.001；LPS6h组,P<0.01),在LPS处理12h后NGAL mRNA恢复到基线水平,LPS12h、LPS24h组与Con组相比无显著差异(P>0.05)。Caspase3mRNA在LPS1h、LPS3h组,即LPS处理后的1-3h内显著升高(LPS1h组,P<0.001：LPS3h组,P<0.05),在LPS处理6h后Caspase3mRNA恢复到基线水平,LPS6h、LPS12h、LPS24h各组与Con组相比无显著差异(P>0.05)；经相关性分析,NGAL mRNA与Caspase3mRNA间存在良好的相关性(r=0.448,P<0.05)。②LPS组NGAL mRNA表达水平显著升高(P<0.001),为Con组的3.177±0.239倍,而Caspase3mRNA亦显著上调(P<0.01),为Con组的2.361±0.287倍；siRNA组NGAL mRNA表达水平显著受到抑制(P<0.01),只为Con组的28.5%,而Caspase3mRNA无显著变化,与对照组相比无显著差异(P>0.05)；siRNA+LPS组NGAL mRNA表达水平也显著受到抑制(P<0.01),但较siRNA组的表达水平略有升高,为对照组的46.6%,但Caspase3mRNA显著升高(P<0.001),为Con组的4.556±0.278倍,并且与siRNA组、LPS组相比也均有显著差异(P<0.001)。③经流式细胞仪检测,Con组具有1.08%的坏死率,具有10.55%的凋亡率；siRNA组坏死率为1.25%,凋亡率为13.71%,与Con组相比均无显著差异(P>0.05)；LPS组坏死率为2.38%,凋亡率为21.53%,与Con组及siRNA组相比均具有显著差异(P<0.001)；siRNA+LPS组坏死率为2.34%,凋亡率为36.06%,该组的坏死率与Con组及siRNA组相比具有显著差异(P<0.001),与LPS组相比无显著差异(P>0.05),该组的凋亡率与其他三组相比均具有显著差异(P<0.001)。④TUNEL检测HK-2细胞凋亡的结果可见：Con组及siRNA组少见阳性凋亡细胞,LPS组阳性凋亡细胞数较多,siRNA+LPS组阳性凋亡细胞数最多。小结：本研究中显示在LPS介导的HK-2细胞损伤中,细胞凋亡是其主要的病理特征；NGAL基因在受损的肾脏小管上皮细胞中能够及时上调表达,并能够抑制Caspase3基因的上调,从而抑制了细胞的凋亡减轻了细胞损伤。这一研究结果为更好的诊断和治疗septic AKI提供了新的思路和靶点。结论：①由LPS可以诱导大鼠出现septic AKI,病理组织学变化以肾小管上皮细胞水肿、微绒毛紊乱为主要表现,并可见细胞凋亡；②当septic AKI发生时,受损的肾小管上皮细胞显著上调表达NGAL mRNA,上调水平与肾组织内的核心炎症因子TNFα的上调水平密切相关；uNGAL水平与肾组织内NGAL mRNA的变化密切相关,真实的反映了肾损伤状态；而pNGAL并不是septic AKI的良好标志物。这一研究结果为能更好的应用NGAL诊断septic AKI提供了新的理论依据；③在LPS介导的肾小管上皮细胞损伤中,细胞凋亡是其主要的病理特征；NGAL mRNA在受损的上皮细胞中能够及时上调表达,并对Caspase3mRNA的上调有显著的抑制作用,从而能够抑制细胞的凋亡减轻了细胞损伤。这一研究结果为更好的诊断和治疗septic AKI提供了新的思路和靶点。更多还原

【Abstract】 Acute kidney injury (AKI; or acute renal failure) is an important issue for patients during critical care, with sepsis being the most common trigger for AKI in the intensive care unit (ICU). Because of the lack of sensitive and specific biomarkers for indicating renal cell injury, the mortality rates for septic AKI have remained high. Recently, genomic, transcriptomic, and proteomic techniques have identified neutrophil gelatinase associated lipocalin (NGAL) as an early marker of AKI. NGAL has been investigated in a range of different clinical settings, such as contrast-induced nephropathy, AKI after cardiac surgery or kidney transplantation and AKI in the critical care setting. Overall, the sensitivity for NGAL to predict AKI is0.815(95%confidence interval,0.732-0.892) and it is a promising biomarker for AKI, similar to troponin for acute myocardial infarction.However, the use of NGAL in detecting or predicting the outcomes of patients with septic AKI is complex and depends on the clinical setting. In previous research of critically ill patients, both serum NGAL (sNGAL) and plasma NGAL (pNGAL) levels have the potential to act as early biomarkers for AKI. While both of them are highly sensitive, they have not been found to be very specific predictors of septic AKI. Shapiro et al assessed the diagnostic accuracy of pNGAL in predicting AKI, wherein it was revealed that pNGAL concentrations of>150ng/mL were96%sensitive but only51%specific for patients with suspected septic AKI. Martensson et al observed that pNGAL is elevated in patients with systemic inflammatory response syndrome, severe sepsis, and septic shock, and it should be used with caution as a marker of AKI in ICU patients with septic shock. In contrast, studies have shown that urinary NGAL (uNGAL) is more useful for predicting AKI, as uNGAL levels are not elevated in septic patients without AKI. Understanding the role of NGAL in impaired renal tissues may help clarify this issue.Furthermore, a biomarker should temporally reflect the pathophysiology initiated by a stimulus leading to injury so as to alert the clinician to a potentially reversible stage of the illness. In the case of septic AKI, the relationship between NGAL and early inflammation mechanisms in the kidney will ought to be clearly established. However, the mechanisms of septic AKI remain undefined. Increasing evidence suggests that intrarenal inflammatory mediators play an important role in the pathogenesis of kidney injury. Specially, tumor necrosis factor a (TNFα) is a pivotal proinflammatory mediator and interleukin (IL)-6is an accessory factor. However, it remains unknown whether NGAL expression is related to changes in renal IL-6and TNFa during the early stage of septic AKI.Based on the available evidence, the use of NGAL as a marker of septic AKI is promising but requires further investigation. In particular, the relationship between NGAL expression, humoral NGAL and renal inflammation requires additional clarification. In addition, the mechanism of NGAL which was expressed in the injured epithelia must be investigated to explain the function of NGAL as acute phase reactive proptein in renal during sepsis.However, few studies have specifically investigated the expression and its mechanism of NGAL in renal tissues during sepsis. Therefore, the purpose of this study was to investigate the pattern and localization of renal NGAL expression, and to explore the relationship between renal inflammation mediators, such as TNFa and IL-6, and humoral NGAL in a rat model of LPS-induced kidney injury, as well as the antiapoptotic mechanism of NGAL was explored in lipopolysaccharide (LPS)-treated HK-2to provide systematic and reliable theoretical base for the application of NGAL in diagnosis and treatment of septic AKI.Part1Preparation of LPS-induced acute kidney injury in ratsObjective:To induce septic AKI by using lipopolysaccharide (LPS,3.5 mg/kg, ip) and evaluate the SCr and kidney pathological changes in order to make clear the acute renal damage.Methods:The rats were divided into six groups according to processing factors and the time difference within24hours. The control group (Con) for salt water treatment which was given0.9%salt water (1ml, ip). The other groups (LPS groups) which were given LPS (3.5mg/kg, ip) were divided into5groups according to treating time (1h,3h,6h,12h,24h). According to the presupposed time points, the animals were anesthetized with pentobarbital sodium to take blood samples to determine SCr and harvest kidney to verify the histological damages under light and electron microscopy.Results:Rats treated with LPS showed significantly elevated levels of SCr, which were significantly increased from3to12hours after LPS administration compared with those in Con group (P<0.01).The kidneys from the Con group showed normal glomeruli and tubules. In contrast, the kidneys of the LPS-treated rats were characterized by transient renal damage. Under a light microscope, there were no intrinsic lesions within the glomeruli, but lesions consisting of epithelial swelling were observed in the3-12-hour groups. Further, intracellular edema was also detected and was more severe in the straight segment of the proximal tubules in the LPS-treated rats. Ultrapathology analysis further demonstrated the presence of intracellular edema, coupled with disarranged microvilli, and/or injury or destruction of the mitochondrial outer membrane in the proximal epithelia.Conclusions:On the basis of changes to serum creatinine levels and renal histology, we were able to confirm LPS-induced AKI, and thus confirm that we had established a suitable animal model. Part2Renal NGAL expression in LPS-induced acute kidney injury in the ratObjective:Neutrophil gelatinase associated lipocalin (NGAL) is a highly predictive biomarker of acute kidney injury. To understand the role of NGAL in renal injury during sepsis, we investigated the temporal changes and biological sources of NGAL in a rat model of acute kidney injury, and explored the relationship between renal inflammation, humoral NGAL and NGAL expression during endotoxemia.Methods:To induce acute renal injury, rats were treated with LPS(3.5mg/kg, ip), and the location of NGAL mRNA was evaluated by in situ hybridization. Quantitative RT-PCR was also used to determine the dynamic changes in NGAL, tumor necrosis factor a (TNFa) and interleukin (IL)-6mRNA’expression1,3,6,12, and24hours following LPS treatment. The correlation among NGAL, TNFa and IL-6was analyzed. Urinary and plasma NGAL (u/pNGAL) levels were measured, and the relationship between humoral NGAL and NGAL expression in the kidney was investigated.Results:Renal function was affected3-12hours after LPS. NGAL mRNA was significantly upregulated in tubular epithelia at the same time (P<0.01). The course of NGAL mRNA upregulation occurred in parallel with renal damage. There was a transient increase in TNFa and IL-6mRNA levels within3hours following LPS administration(P<0.01),and a strong correlation between TNFa and NGAL mRNA (r=0.995, P<0.001) but not with IL-6mRNA. Both pNGAL and uNGAL levels were markedly increased compared with those in the control group (P<0.01); however, only uNGAL levels were correlated with NGAL mRNA (r=0.850, P<0.001).Conclusions:NGAL mRNA upregulation is sensitive to LPS-induced renal TNFa increase and injury, which are observed in the tubular epithelia. Urinary NGAL levels accurately reflect changes in NGAL in the kidney. Part3Exploration of the antiapoptotic mechanism of NGAL in LPS-treated HK-2Objective:NGAL mRNA has been found to be up-regulated in renal epithelia during endotoxemia in our previous study. To understand the role of NGAL in renal epithelium during sepsis, we investigated the temporal changes of NGAL in LPS-treated HK-2, and explored the relationship between NGAL mRNA and Caspase3mRNA. Furthermore, we investigate whether specific inhibition targeting NGAL using small interfering RNA (siRNA) would provide renal protection by reducing apoptosis in LPS-treated HK-2.Methods:An HK-2cell model was used, in which NGAL mRNA and Caspase3mRNA were evaluated by qRT-PCR, and the correlation among them was analyzed as well. In vitro delivery of siRNA was performed to investigate whether NGAL could protect HK-2from LPS-induced injury by inhibiting cell apoptosis.Results:①The expression of NGAL mRNA was upregulated within6hours after LPS50uM treatment in HL-2(LPS1h and LPS3h groups, P<0.001; LPS6h group, P<0.01), and decreased to baseline after12hours (P>0.05). The expression of Caspase3mRNA was upregulated within3hours after LPS (LPS1h group, P<0.001; LPS3h group, P<0.05), and decreased to baseline after6hours (P>0.05). There was a strong correlation between Caspase3and NGAL mRNA (r=0.448, P<0.05).②The transfection of siRNA effectively interfered the expression of NGAL mRNA (P<0.001). The expression of NGAL mRNA decressed to35%level of Con group in siRNA group, and46%level in siRNA+LPS group. The expression of Caspase3mRNA was significantly upregulated in siRNA+LPS relative to Con, LPS and siRNA groups (P<0.001).③We have detected the necrosis and apotosis in HK-2after transfection by flow cytometry.There was1.08%necrosis and10.55%apoptosis in Con group. The necrosis was1.25%, apoptosis was13.71%in siRNA group, and there was no significant difference relative to Con. There were significant increase of necrosis (2.38%) and apoptosis(21.53%) in LPS relative to Con and siRNA groups (P<0.001) There were significant increase of necrosis (2.34%) in siRNA+LPS relative to Con and siRNA groups (P<0.001), but not to LPS group (P>0.05). However, the apoptosis (36.06%) of siRNA+LPS has significantly changes relative to Con, LPS and siRNA groups (P<0.001). There was a transient increase in TNFa and IL-6mRNA levels within3hours following LPS administration, and a strong correlation between TNFa and NGAL mRNA (r=0.995, P<0.001) but not with IL-6mRNA. Both pNGAL and uNGAL levels were markedly increased compared with those in the control group (P<0.001); however, only uNGAL levels were correlated with NGAL mRNA (r=0.850, P<0.001).④We detected the apoptosis in the four groups by TUNEL stain as well. There was seldom apoptosis in Con and siRNA groups, more apoptosis in LPS group and most apoptosis in siRNA+LPS.Conclusions:This study reveals that apoptosis is the main pathological reaction in LPS-treat HK-2. NGAL mRNA upregulation is sensitive to LPS treatment, and NGAL can inhibit the increase of Caspase3mRNA. So, NGAL can protect HK-2from apoptosis which is induced by LPS.From the existing research results, we drew the following conclusions through the experimental observation in LPS-induced septic AKI in rats and LPS-treated HK-2cells.①LPS can induce septic AKI in rats, and the main pathological histology is showed in epithelia including edema, microvilli disarray and apoptosis.②NGAL mRNA upregulation is sensitive to LPS-induced renal TNFa increase and injury, which are observed in the tubular epithelia; Urinary NGAL levels accurately reflect changes in NGAL in the kidney, so it is an ideal biomarker of septic AKI; Plasma NGAL is not yet perfected because it is not correlated with NGAL mRNA in renal. The results can provide a new theory basis of better application for NGAL in septic AKI diagnosis.③Apoptosis is the main pathological reaction in LPS-treat HK-2. NGAL mRNA upregulation is sensitive to LPS treatment, and NGAL can inhibit the increase of Caspase3mRNA. So, NGAL can protect HK-2from apoptosis which is induced by LPS. This study results provide new ideas and targets for improving diagnosis and treatment of septic AKI.更多还原