血红素氧合酶-1基因转染对器官移植的作用研究

血红素氧合酶(heme oxygenase,HO)是体内唯一催化血红素分解代谢的限速酶,可以氧化降解血红素,将其分解为CO、Fe2+和胆绿素.HO有3种同工酶,其中HO-1是血红素降解的起始酶和限速酶,是唯一可以被诱导的HO.HO-1作为移植器官存活的关键"保护基因",通过基因转染使其稳定过表达,能显著减轻移植器官的缺血再灌注损伤,提高移植物存活率.参33     

血红素氧合酶-1抑制T淋巴细胞对血管内皮细胞的粘附作用

目的研究血红素氧合酶-1(HO-1)抑制T淋巴细胞对血管内皮细胞的粘附作用。方法采用脂质体介导基因转染技术将PcDNA3-HO-1质粒转入血管内皮细胞。用间接免疫荧光技术在蛋白质水平检测HO-1在血管内皮细胞上的表达;用γ-干扰素(INF-γ)活化血管内皮细胞;用CFSE标记植物血凝素(PHA)活化的JurkatT细胞;采用粘附阻断实验观察转染HO-1的血管内皮细胞和JurkatT细胞间的粘附作用。结果HO-1可在人血管内皮细胞系中稳定表达;转染HO-1的活化内皮细胞与JurkatT细胞的粘附作用显著下降,CFSE标记的阳性率为21.24%,而未转染的对照组CFSE标记的阳性率为56.16%,两组相比,差异有统计学意义(P<0.05);应用HO-1抑制剂ZnPP后,粘附抑制作用消失。结论HO-1可以明显抑制T淋巴细胞对血管内皮细胞的粘附作用。     

大鼠胰岛转染人血红素氧合酶-1基因对同种胰岛移植的影响

目的探讨大鼠胰岛转染人血红素氧合酶-1(HO-1)基因在胰岛移植中的潜在应用价值。方法采用携带人HO-1基因的腺病毒对新分离的SD大鼠胰岛细胞进行转染;对体外培养的胰岛细胞使用重组人肿瘤坏死因子α及放线菌酮诱导凋亡。使用流式细胞术检测凋亡率;每只链脲霉素诱导的糖尿病模型大鼠门静脉内置入约1200个胰岛当量的胰岛后,观察糖尿病大鼠血糖及体重变化;免疫组织化学法检测肝内移植胰岛细胞的胰岛素、HO-1蛋白表达及表达CD3抗原的淋巴细胞浸润情况。结果转染人HO-1基因的胰岛细胞凋亡率明显低于对照组(P<0.05);单纯胰岛细胞移植后移植物存活时间为(5.33±4.18)d,转染人HO-1基因的胰岛细胞移植后移植物存活时间为(10.56±4.33)d,两组比较,P<0.05;转染人HO-1基因的胰岛细胞培养48 h即见人HO-1蛋白表达;肝内移植7 d后移植物有人HO-1蛋白表达;移植胰岛周边及胰岛内淋巴细胞浸润程度较单纯胰岛移植组明显减轻。结论大鼠胰岛转染人HO-1基因能够增加体外培养胰岛细胞的抗凋亡能力,并能延长体内移植胰岛的存活时间,减轻淋巴细胞对胰岛的浸润。     

移植物转染血红素氧合酶-1基因抑制慢性移植物血管病

目的探讨移植物转染血红素氧合酶-1（HO-1）基因对慢性移植物血管病的影响。方法克隆HO-1基因，并构建含有HO-1基因的重组腺病毒载体（Ad-HO-1），实验分为4组：A组为同系移植对照组，供、受者均为Lewis大鼠，无特殊处理；B组为同种移植对照组，Lewis大鼠接受未经处理的BN大鼠胸主动脉移植；C组为同种移植空载体对照组，Lewis大鼠接受以空载体（不含HO-1基因）处理的BN大鼠的胸主动脉移植；D组为同种移植实验组，Lewis大鼠接受转染HO-1基因的BN大鼠的胸主动脉移植。于移植后60d取移植动脉，进行组织形态学观察，测量内膜厚度；免疫组化和逆转录聚合酶链反应检测HO-1在移植动脉中的表达。结果A组移植动脉形态正常；B组、C组移植动脉呈移植物血管病表现，血管内膜显著增厚，D组移植动脉呈内膜炎改变，内膜厚度与B组、C组相比，差异有统计学意义（P〈0．01）。免疫组化及RT-PCR检测显示，与A组、B组和C组相比，D组移植动脉可以检测到HO-1基因及其蛋白表达。结论在移植血管中预先转染HO-1基因，能明显缓解移植动脉的纤维化进程以及内膜的增生，对慢性排斥反应所致的移植物血管病具有抑制作用。     

短发夹RNA沉默血红素氧合酶-1基因表达对胃癌细胞系SGC-7901生物学行为的影响

目的 观察血红素氧合酶-1(HO-1)基因沉默对胃癌细胞系SGC-7901生长、增殖的影响.方法 构建靶向HO-1的短发夹RNA(shRNA-HO-1)干扰质粒转染人胃癌细胞系SGC-7901,逆转录-聚合酶链反应(RT-PCR)、细胞免疫化学分别在mRNA、蛋白质水平检测抑制效果.流式细胞仪和噻唑蓝(MTT)检测HO-1基因沉默后细胞的细胞周期和生长情况.结果 shRNA-HO-1在mRNA、蛋白质水平高效特异地抑制了细胞SGC-7901中HO-1的表达(抑制率分别为62.4%、67.6%);较对照质粒组,HO-1的表达被抑制后,G0/G1期细胞百分比明显减少(52.025±1.638比67.525±1.938,P<0.05),细胞生长受抑制[2.036±0.072比2.783±0.067(72 h A值),P<0.05].结论 shRNA-HO-1可有效抑制胃癌细胞中HO-1的表达;HO-1的表达减少抑制肿瘤细胞生长.     

转染人血红素加氧酶-1基因抑制移植静脉血管内膜增生

目的　应用含人血红素加氧酶 - 1基因 (human Heme Oxygenase- 1,h HO- 1)的重组腺病毒 (Adeno- XTMh HO- 1,Ad- h HO- 1)转染静脉移植血管 ,观察 h HO- 1基因预防静脉移植血管内膜增生的作用。　方法　将 2 1只日本大耳白兔分为 3组 ,对照组 ,Ad- null组和 Ad- h HO- 1组 ,每组各 7只。在兔颈外静脉移植于颈总动脉的血管移植术前分别应用肝素生理盐水、Ad- null和 Ad- h HO- 1病毒液常温浸泡静脉移植血管 30 min。术后 2 8d病理切片观察移植血管内膜增生的情况 ,计算机图象分析仪计算新生内膜厚度、中膜厚度及二者比值 ;采用免疫组织化学染色方法 (S- P法 )观察术后 14 d、2 8d移植血管壁 h HO- 1蛋白表达情况。　结果　Ad- h HO- 1组内膜厚度、内膜厚度与中膜厚度比均显著低于Ad- null组和对照组 (P<0 .0 1) ,中膜厚度差别无统计学意义 (P>0 .0 5 )。 Ad- h HO- 1组静脉血管壁细胞 h HO- 1免疫组化染色阳性。　结论　 Ad- h HO- 1转染兔静脉旁路移植血管能够抑制内膜增生。     

血红素加氧酶-1对器官移植保护作用的研究进展

血红素加氧酶-1(heme oxygenase,HO-1)是机体血红素降解过程的限速酶,它可将血红素分解为一氧化碳(CO)、游离铁和胆绿素.目前HO-1及其降解血红素的代谢产物体系在抗氧化、抗凋亡、抗炎症、舒张血管及细胞保护等方面的作用受到了普遍关注.HO-1在器官移植中的作用已成为研究热点,现就HO-1在器官移植中细胞保护作用的研究进展作如下综述.     

大鼠血红素加氧酶-1基因转染对大鼠心肌缺血再灌注损伤的影响

目的 评价重组腺相关病毒(rAAV)介导大鼠血红素加氧酶-1(rHO-1)基因转染在大鼠心肌缺血再灌注损伤的影响及其机制.方法 健康雄性SD大鼠81只,体重220～280 g,随机分为4组:假手术组(SH组,n=9)、生理盐水组(NS组,n=24)、重组腺相关病毒-荧光蛋白组(rAAV-EGFP组,n=24)和重组腺相关病毒-HO-1组(rAAV-HO)-1组,n=24).NS组、rAAV-EGFP组和rAAV-HO-1组分别心肌注射600 μl生理盐水、rAAV-EGFP(1.5×1011 v.g.)或rAAV-HO-1(1.5×1011 v.g.).在基因转染后3个月,NS组、rAAV-EGFP组和rAAV-HO-1组各处死3只大鼠,取注射部位心肌,通过测定心肌细胞荧光蛋白的表达,计算转染率,并通过免疫组化染色和RT-PCR法检测HO-1蛋白和HO-1 mRNA的表达.采用结扎左冠状动脉前降支30 min,再灌注120 min的方法建立心肌缺血再灌注模型;再灌注120 min后,处死大鼠,测定心肌组织超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量,电镜下观察心肌细胞的超微结构.结果 心肌细胞转染率为(53.5±2.0)%.与NS组比较,rAAV-HO-1组HO-1蛋白及HO-1 mRNA表达增加(P＜0.01);与rAAV-EGFP组比较,rAAV-HO-1组HO-1蛋白及HO-1 mRNA表达增加(P＜0.01);与SH组比较,NS组和rAAV-EGFP组SOD活性下降,MDA含量升高(P＜0.01);与NS组和rAAV-EGFP组比较,rAAV-HO-1组SOD活性升高,MDA含量降低(P＜0.01).NS组及rAAV-EGFP组心肌细胞超微结构损伤较SH组和rAAV-HO-1组重.结论 腺相关病毒介导的血红素加氧酶-1基因转染大鼠心肌细胞后,可减轻心肌缺血再灌注损伤,其机制与抗氧化有关.     

血红素加氧酶-1系统和心脏移植

血红素加氧酶(血红素氧化酶，heme oxygenase,HO)是血红素降解的起始酶和限速酶，催化血红素降解为胆色素、CO和自由铁，在体内以HO-1、HO-2、HO-3三种形式存在，HO-1为诱导型，另外两种为组成型。血红素是HO-1的主要作用底物，各种非血红素因素包括重金属、细胞因子、激素、内毒素、热休克、化学物质及氧化刺激等均可诱导HO-1大量表达。     

转染血红素氧合酶—1基因减轻人肝细胞体外缺氧—复氧损伤

目的 探讨血红素氧合酶-1重组腺病毒载体(Ad-HO-1)体外转染人肝细胞的转染效果及其对肝细胞缺氧-复氧损伤的影响.方法 取人肝细胞系L-02细胞,滴加低温保存的Ad-HO-1,分别培养24 h、48 h和72 h(24 h组、48 h组和72 h组),并以加入空载体腺病毒共培养的L-02细胞为空白对照.采用逆转录聚合酶链反应法检测各组肝细胞HO-1 mRNA的表达水平;以间接免疫荧光标记法检测各组肝细胞的HO-1表达率;在倒置荧光显微镜下观察转染24 h和72 h的肝细胞中绿色荧光蛋白(EGFP)的表达.取空白对照组肝细胞(培养48 h)和48 h组肝细胞,缺氧培养4 h后再有氧培养8 h,采用四甲基偶氮唑盐法测定两组肝细胞存活率.结果 24 h组、48 h组和72 h组HO-1 mRNA表达水平明显高于空白对照组,且随着转染时间的延长,HO-1 mRNA的表达水平逐渐升高.空白对照组HO-1的表达率为2.0%,24 h组为29%,48 h组为85.6%,72 h组为84.6%.基因转染后24 h和72 h,可以观察到L-02细胞中EGFP的表达.经历缺氧-复氧实验后,空白对照组肝细胞的存活率为(37.7±3.5)%,48 h组肝细胞的存活率为(89.4±5.2)%,二者相比较,差异有统计学意义(P<0.01).结论 Ad-HO-1在体外能有效的转染人肝细胞;与未转染者相比,转染肝细胞的缺氧-复氧损伤程度较轻.     

Effect of HO-1 cDNA-liposome complex transfer on erectile signalling of aged rats

This work aimed to assess the efficacy of haeme oxygenase-1 (HO-1) cDNA-liposome complex transfer as a mediator of erectile signalling in aged rats. One hundred and fifty aged white albino rats were equally divided into five groups: controls, rats receiving lipofectamine, rats receiving intracorporeal HO-1 cDNA-lipsome complex, rats receiving HO-1 cDNA-liposome complex plus nitric oxide synthase (NOS) inhibitor, and rats receiving HO-1 cDNA-liposome complex plus HO inhibitor. Six rats were killed from each group after 12, 24 and 48 h, and after1 and 2 weeks. In dissected cavernous tissues, the following were assessed: HO-1 gene expression, Western blot for HO-1, HO enzyme activity, cGMP and histopathology. The results showed that HO-1 cDNA-liposome complex transfer led to a significant increase in cavernous tissue HO-1 protein, HO-1 gene expression, HO enzyme activity and cGMP up to 1 week. NOS inhibition exhibited no effect on HO-1 gene enhancement of cavernous tissue HO enzyme activity or cGMP, whereas inhibition of HO significantly decreased these parameters. Histopathology of cavernous tissue demonstrated a significant dilatation of helicine arteries in HO-1 cDNA-liposome complex treated group after 48 h compared with the controls. It is concluded that HO-1 cDNA-liposome complex transfer augments cavernous tissue cGMP with subsequent sinusoidal relaxation.     

Gene Transfer of Heme Oxygenase-1 and Carbon Monoxide Delivery Inhibit Chronic Rejection

The hallmark of chronic rejection is the occlusion of the artery lumen by intima hyperplasia as a consequence of leukocyte infiltration and vascular smooth muscle cell (VSMC) migration and proliferation. Heme oxygenase-1 (HO-1) is a tissue protective molecule which degrades heme into carbon monoxide (CO), free iron and biliverdin. We analyzed the effects of HO-1 gene transfer into the vessel wall using an adenoviral vector (AdHO-1) and of CO delivery in a model of chronic allogeneic aorta rejection in rats. Carbon monoxide treatment was achieved by a new pharmacological approach in transplantation using methylene chloride (MC), which releases CO after degradation. AdHO-1-mediated gene transfer into aorta endothelial cells (ECs) or CO delivery resulted in a significant reduction in intimal thickness compared to untreated or noncoding adenovirus-treated controls. Aortas transduced with AdHO-1 or treated with CO showed a reduction in the number of leukocytes as well as in the expression of adhesion molecules, costimulatory molecules and cytokines, with the gene transfer treatment displaying a more pronounced effect than the CO treatment. Conversely, CO inhibited VSMC accumulation in the intima more efficiently than AdHO-1 treatment. Gene transfer of HO-1 and pharmacological manipulation of CO are novel approaches to the analysis and treatment of chronic rejection.     

Inhibition of graft arteriosclerosis development in rat aortas following heme oxygenase-1 gene transfer

Heme oxygenase 1 (HO-1) is an enzyme which degrades heme into tree end products: biliverdin, free iron and carbon monoxide. This enzyme has recently been shown to have anti-inflammatory and tissue protective effects. HO-1 expression is involved in organ protection in pathological situations, and immunosuppressive treatments resulting in indefinite graft survival without chronic rejection have been associated with HO-1 expression by cells of the vessel wall. The aim of this study was to analyze the effect of specific HO-1 overexpression. We used a recombinant adenovirus coding for human HO-1 cDNA in a rat aorta chronic rejection model, 30 days after transplantation. Control groups included rats non treated or treated with a non-coding adenovirus Addl324. We first demonstrated that AdHO-1 was efficiently expressed in endothelial cells in vitro, and in rat aortas ex vivo after adenovirus gene transfer. We found that intimal thickening in AdHO-1 treated aortas (10.8 +/- 3.8%, n=5) was significantly decreased compared to untreated (21.2 +/- 5.6%, n = 5) or Addl324-treated (21.1 +/- 1.2%, n = 4) aortas. Immunohistology showed that treatment with AdHO-1 resulted in a significant reduction in leukocyte infiltration and a decreasing number of VSMC in the intima, compared to Addl324-treated aortas. However, this effect of HO-1 on chronic rejection did not imply modifications on numbers of apoptotic cells in the graft or of alloantibody levels. We have demonstrated, for the first time, that specific HO-1 overexpression following gene transfer of HO-1 inhibited chronic rejection by reducing leukocyte and VSMC infiltration of the aorta intima.     

Heme oxygenase-1 attenuates epithelial-to-mesenchymal transition of human peritoneal mesothelial cells

Background

Epithelial-to-mesenchymal transition (EMT) of peritoneal mesothelial cells has been regarded as an early mechanism of peritoneal fibrosis. A substantial and rapidly growing literature indicates that HO-1 provides the provenance for pathways that can interrupt virtually all major mechanisms of tissue injury. The effects of HO-1 expression on EMT, which plays a critical role in the development of peritoneal membrane (PM) fibrosis, are unknown and its roles in peritoneal fibrosis has not been studied, yet.

Methods

A piece of human omentum obtained from consenting patients undergoing elective abdominal surgery was used for study. We treated the human peritoneal mesothelial cells (HPMCs) with high glucose solution and HO-1 inducer (hemin, 10 μmol/L). To further investigate the pure effect of HO-1 on EMT of mesothelium, gene transfer of recombinant Adenovirus-harboring human HO-1 (Adv-HO-1 gene) to HPMCs was done.

Results

Exposure of HPMCs to HG solution resulted in an increase of the expression of mesenchymal markers such as α-smooth muscle actin (α-SMA) and was associated with a decrease in the expression of epithelial markers, E-cadherin. HO-1 protein expression was decreased in the same situation. Treatment of HPMCs with HO-1 inducer, hemin showed a dosage-dependent amelioration of HG induced changes in markers of EMT with increase of expression of HO-1. Human HO-1 gene transfection resulted in a significant increase in HO-1 expression and ameliorated HG-induced changes in expression of E-cadherin and α-SMA.

Conclusion

Taken together, our results suggest that HO-1 has a critical role in the modulation of peritoneal fibrosis, and, more important, the suppression of EMT. This study is the first to show the beneficial effect of HO-1 on reversing EMT in MC.     

Gene transfer of immunomodulatory peptides correlates with heme oxygenase-1 induction and enhanced allograft survival

BACKGROUND: Decapeptides derived from human HLA class I sequences have been shown to prolong allograft survival. The mechanism of action of these peptides has been uncertain, because they act in an MHC unrestricted manner. Recently, it was found that these peptides bind heme oxygenase 1 (HO-1). In the present study, we sought to determine whether local delivery of these peptides through gene transfer could extend allograft survival, and to explore the underlying mechanisms. METHODS: C57BL/6 neonatal hearts were transplanted to CBA/J recipients and the peptide, or plasmid DNA encoding the peptide, was injected directly into the allograft at the time of the transplant. RESULTS: Direct injection of 1 microg of the B2702 peptide into the allograft did not prolong survival (13.3+/-0.8 vs. 13.4+/-0.8 days for untreated controls), but injection of 400 microg of peptide did extend survival (22.0+/-0.6). Injection of plasmid DNA encoding the B2702 peptide was superior to peptide delivery, extending graft survival to 30.8+/-1.5 days. Similar results were obtained using another plasmid encoding the rationally designed peptide BC1 (28.5+/-1.7), whereas no significant prolongation was observed using a plasmid encoding the control peptide B2705 (16.5+/-1.0). To explore the hypothesis that these peptides exert their immunosuppressive effect by altering HO-1 activity, animals were treated with iron protoporphyrin, an inducer of HO-1 activity, or tin protoporphyrin, an inhibitor of HO-1. Treatment with iron protoporphyrin alone extended graft survival (24.5+/-1.6) and did not alter the benefit in survival seen with BC1 gene transfer (28.0+/-0.8). In contrast, treatment with tin protoporphyrin abolished the benefit of BC1 gene transfer (17.0+/-0.6). CONCLUSIONS: These results demonstrate that plasmid mediated gene transfer is an effective means for delivering immunosuppressive peptides to extend allograft survival. The experiments suggest that these peptides may act by increasing HO-1 activity and support a role for HO-1 in immune regulation and allograft survival.     

血红素氧合酶1基因转移对大鼠肾缺血再灌注损伤的防护作用

目的探讨血红素氧合酶1(HO-1)基因转移对大鼠自体移植肾缺血再灌注损伤的保护作用。方法构建HO-1腺病毒表达载体,经肾动脉灌注转染26只大鼠(实验组)移植肾,4℃保存24h后行自体移植,移植后5d切除对侧肾脏;以25只大鼠为对照。于移植后3h、3d,应用逆转录聚合酶链反应(RT-PCR)及免疫组织化学方法检测移植肾HO-1基因及蛋白的表达;应用酶联免疫吸附试验(ELISA)法测定肾组织匀浆中HO-1蛋白的含量(以吸光度值表示)。结果移植后3h及3d,实验组移植肾HO-1mRNA的表达强度分别为0·65±0·11及0·86±0·17,而对照组分别为0·09±0·01及0·15±0·02,两组相比差异具有统计学意义(t=14·38,11·73,P均<0·05);实验组移植肾HO-1蛋白含量分别为(297±61)及(468±51)ng/g,而对照组分别为(98±30)及(155±31)ng/g,两组相比差异具有统计学意义(t=8·27,14·83,P均<0·05)。与对照组相比实验组移植肾病理改变明显减轻(P<0·05),血肌酐水平明显降低(t=8·41,P<0·05)。结论腺病毒载体可成功介导HO-1基因对大鼠肾脏的转移,对自体移植肾缺血再灌注损伤具有保护作用。     

重组腺相关病毒介导血红素加氧酶-1基因转染对大鼠离体心脏缺血再灌注损伤时炎性细胞因子的影响

目的 探讨重组腺相关病毒(rAAV)介导血红素加氧酶-1(HO-1)基因转染对大鼠离体心脏缺血再灌注损伤时炎性细胞因子的影响.方法 健康雄性SD大鼠30只,体重220～280 g,随机分为3组:对照组(C组,n=6),生理盐水组(N组,n=12)和rAAV-HO-1组(H组,n=12).N组和H组分别心肌注射600μl生理盐水或rAAV-HO-1(1.5×10~(11)v.g.).基因转染后3个月,N组和H组各处死6只大鼠,取注射部位心肌组织,测定HO-1的表达.制备大鼠离体心脏缺血再灌注模型,于平衡灌注15 min,再灌注15、30、45 min时,记录左心室舒张末压(LVEDP)、左心室收缩压(LVSP)、左心室收缩压最大上升速率(+dp/dt_(max))和左心室收缩压最大下降速率(-dp/dt_(max)),测定心肌组织肿瘤坏死因子α(TNF-α)和白细胞介素6(IL-6)的含量.结果 H组心肌组织HO-1表达较N组上调(P<0.01).与C组比较,N组和H组再灌注各时点LVEDP、心肌组织TNF-α和IL-6的含量升高,LVDP和±dp/dt_(max)均降低(P<0.05或0.01);与N组比较,H组LVEDP、心肌组织TNF-α和IL-6的含量降低,LVSP和±dp/dt_(max)均升高(P<0.05或0.01).结论 rAAV介导HO-1基因转染大鼠心肌后,可减轻离体心脏缺血再灌注损伤,其机制与抑制炎性细胞因子的生成有关.     

Systemic expression of heme oxygenase-1 ameliorates type 1 diabetes in NOD mice

Heme oxygenase-1 (HO-1) is an enzyme with potent immunoregulatory capacity. To evaluate the effect of HO-1 on autoimmune diabetes, female NOD mice at 9 weeks of age received a single intravenous injection of a recombinant adeno-associated virus bearing HO-1 gene (AAV-HO-1; 0.5 x 10(10)-2.5 x 10(10) viruses/mouse). In a dose-dependent manner, HO-1 transduction reduced destructive insulitis and the incidence of overt diabetes examined over a 15-week period. HO-1-mediated protection was associated with a lower type 1 T-helper cell (Th1)-mediated response. Adaptive transfer experiments in NOD.scid mice demonstrated that splenocytes isolated from AAV-HO-1-treated mice were less diabetogenic. Flow cytometry analysis revealed no significant difference in the percentages of CD4(+)CD25(+) regulatory T-cells between saline-treated and AAV-HO-1-treated groups. However, the CD11c(+) major histocompatibility complex II(+) dendritic cell population was much lower in the AAV-HO-1-treated group. A similar protective effect against diabetes was observed in NOD mice subjected to carbon monoxide (CO) gas (250 ppm CO for 2 h, twice per week). These data suggest that HO-1 slows the progression to overt diabetes in pre-diabetic NOD mice by downregulating the phenotypic maturity of dendritic cells and Th1 effector function. CO appears to mediate at least partly the beneficial effect of HO-1 in this disease setting.     

Plasma and urinary heme oxygenase-1 in AKI

AKI induces upregulation of heme oxygenase 1 (HO-1), which exerts cytoprotective effects and modulates the renal response to injury, suggesting that a biomarker of intrarenal HO-1 activity may be useful. Because HO-1 largely localizes to the endoplasmic reticulum and has no known secretory pathway, it is unclear whether plasma or urinary levels of HO-1 reflect intrarenal HO-1 expression. We measured plasma and urinary levels of HO-1 by ELISA during the induction and/or maintenance phases of four mouse models of AKI: ischemia/reperfusion, glycerol-induced rhabdomyolysis, cisplatin nephrotoxicity, and bilateral ureteral obstruction. In addition, we measured levels of HO-1 mRNA and protein in the renal cortex. Each AKI model increased renal HO-1 gene expression, which corresponded with release of HO-1 into plasma and urine by 4 hours. Over time, the magnitudes of plasma and urinary HO-1 paralleled renal cortical gene expression. AKI and the associated uremia did not seem to affect extrarenal HO-1 gene activity assessed in the liver, lung, and spleen. In iron-challenged, cultured proximal tubule cells, we observed a positive correlation between HO-1 mRNA level and HO-1 release. In humans, 10 patients with AKI demonstrated markedly higher levels of plasma and urine HO-1 levels than 10 critically ill patients without AKI or 20 patients with CKD or ESRD. In summary, these data suggest that plasma and urinary HO-1 levels may serve as biomarkers of AKI and intrarenal HO-1 gene activity.