Amelioration of cisplatin-induced acute kidney injury by recombinant neutrophil gelatinase-associated lipocalin

We investigated the protective effect and mechanism of neutrophil gelatinase-associated lipocalin (NGAL) in a murine model of cisplatin-induced nephrotoxicity. Male Swiss-Webster mice were assigned to four groups (n?=?10 in each group). Control mice received vehicle only. Mice in the experimental group were given a single intraperitoneal injection of cisplatin (20?mg/kg) to induce nephrotoxicity, and were divided into three groups. The first group received 100?μL of saline only via tail vein at the time of cisplatin administration. The second group was given biologically active recombinant NGAL via tail vein (250?μg/100?μL solution). The third group was injected with a 250?μg/100μL solution of inactivated NGAL. After 4 days, we measured serum creatinine and urinary N-acetyl-β-d-glucosaminidase (NAG), and performed histologic studies. Biologically active NGAL significantly blunted the rise in serum creatinine (NGAL plus cisplatin 1.33?±?0.31 versus cisplatin alone 2.43?±?0.31?mg/dL, p?<?.001) as well as the increase in urine NAG (NGAL plus cisplatin 60.7?±?14.2 versus cisplatin alone 120.5?±?22.5 units/gm creatinine, p?<?.005). In addition, NGAL conferred a marked reduction in tubule cell necrosis and apoptosis (NGAL plus cisplatin 6.9?±?1.2 versus cisplatin alone 15.1?±?3.4 TUNEL positive nuclei per 100 cells, p?<?.001). These beneficial effects were completely abolished when heat-inactivated NGAL was administered instead of the biologically active form. Since induction of NGAL in kidney tubules is a known physiologic response to cisplatin, the pharmacologic use of NGAL to prevent cisplatin nephrotoxicity is likely to be safe and effective.     

心脏术后尿中性粒细胞明胶酶相关脂质运载蛋白和白细胞介素18与急性肾损伤的关系

目的 探讨接受体外循环心脏手术患者尿中性粒细胞明胶酶相关脂质运载蛋白（NGAL）和尿白细胞介素18（IL-18）与急性肾损伤（AKI）的关系。 方法 根据AKI的诊断标准，将33例体外循环心脏手术的患者分为AKI组及非AKI组，分别留取术前及术后不同时间点的血液和尿液标本，测定Scr、尿NGAL和IL-18水平。 结果 33例中有9例发生AKI，发生率为27.27%。AKI组Scr升高峰值出现在12～48 h内。与术前相比， AKI组术后2 h、4 h尿NGAL及IL-18水平升高，差异有统计学意义（P < 0.01）。与非AKI组比较，AKI组术后各时间点的尿NGAL水平、术后2 h及4 h的尿IL-18水平都较高，差异有统计学意义（P < 0.01）。经尿肌酐（Ucr）校正后，相应时间点的NGAL/Ucr和IL-18/Ucr差异仍有统计学意义（P < 0.01）。术后2 h尿NGAL和尿NGAL/Ucr的界定（cutoff） 值分别在250 µg/L和250 µg/mmol时；术后2 h尿IL-18和尿IL-18/Ucr的界定值分别在1800 ng/L和1800 ng/mmol时，体现出较好的敏感性和特异性。 AKI组术后12 h Scr水平与术后2 h尿NGAL水平呈正相关（r = 0.638，P < 0.05）。结论 体外循环下接受心脏手术的患者AKI发生率较高；术后2 h尿NGAL和NGAL/Ucr、术后2 h尿IL-18和尿IL-18/Ucr当达到一定界定值时，均可作为体外循环下心脏手术后AKI发生的早期诊断参考指标，其中术后2 h尿NGAL/Ucr为250 µg/mmol时更敏感。     

Exogenous normal lymph alleviates lipopolysaccharide-induced acute kidney injury in rats

Abstract

Background: Acute kidney injury (AKI) is a common pathological process which occurs in hemorrhage, intoxication, etc. It has been shown that the lymphatic circulation plays an important regulatory role in the pathogenesis of hemorrhage shock, and that exogenous normal lymph (ENL) has a beneficial effect on multiple organ injuries. In the present study, we investigated the effect of ENL on lipopolysaccharide (LPS)-induced AKI in rats. Methods: The AKI was induced by the jugular vein injection of LPS (iv, 15?mg/kg). After 15?min of LPS injection, saline or ENL without cell components (5?mL/kg) was iv infused at the speed of 0.5?mL per minute. Then, the renal function indices in plasma and renal histomorphology, and the levels of P-selectin, intercellular adhesion molecule-1 (ICAM-1), myeloperoxidase (MPO) and Na⁺-K⁺-ATPase in renal tissue were assessed at 3 or 6?h after LPS injection. Results: LPS induced a severe kidney injury including increased levels of urea, creatinine in plasma, aggrandized activities of ICAM-1 and MPO in renal tissue, and decreased the Na⁺-K⁺-ATPase activity in renal cells. These deleterious effects of LPS were significantly ameliorated by ENL treatment. Conclusion: The present results indicate that ENL protect against LPS-induced AKI, suggesting an alternative therapeutic strategy for treatment of kidney injury accompanied with severe infection or sepsis.     

Changes in renal markers and acute kidney injury after marathon running

Background: The impact of marathon running on kidney function has not been previously described. Methods: From 425 marathon runners, 13 women and 12 men were randomly selected and cardiovascular magnetic resonance imaging (MRI) and blood/urine biomarkers were performed 4 weeks before (baseline), immediately after (peak), and 24 h after the race (recovery). Results: Participants were 38.7 ± 9.0 years old and completed the marathon in 256.2 ± 43.5 min. A total of 10/25 (40.0%) met the Acute Kidney Injury Network definition of acute kidney injury (AKI) based on a rise in serum creatinine. There were parallel and similar mean rises in serum creatinine and cystatin C from baseline, to peak, and return to normal in recovery. Urine neutrophil gelatinase‐associated lipocalin rose from 8.2 ± 4.0 to 47.0 ± 28.6 and returned to 10.6 ± 7.2 ng/mL, P < 0.0001. Likewise, the mean urinary kidney injury molecule‐1 levels were 2.6 ± 1.6, 3.5 ± 1.6 and 2.7 ± 1.6 ng/mL (P = 0.001). The mean and minimum pre‐ and post‐IVC (inferior vena cava) diameters by MRI were 24.9, 18.8 and 25.3, 17.5 mm, respectively, suggesting that runners were not volume depleted at the first post‐race measurement. Conclusion: Approximately 40% of marathon runners experience a transient rise in serum creatinine that meets criteria of AKI with a parallel elevation of cystatin C, and supportive elevations of neutrophil gelatinase‐associated lipocalin and kidney injury molecule‐1 in the urine. All biomarker elevations resolved by 24 h. These data suggest that AKI with a transient and minor change in renal filtration function occurs with the stress of marathon running. The impact of repetitive episodes of AKI with long‐distance running is unknown.     

急性肾损伤生物学标志物在心脏外科术后的研究进展

急性肾损伤是心脏外科手术后常见的严重并发症,发病率和病死率均较高.血肌酐及尿量作为急性肾损伤的标志物缺乏敏感性,延误了早期有效的治疗.近年来对于诊断急性肾损伤的生物学标志物方面的研究取得了较大进展,有些指标已逐步进入临床研究阶段,其中包括中性粒细胞明胶酶相关脂质运载蛋白、胱抑素C、肾损伤分子-1、白细胞介素-18等.本文旨在对心脏外科术后急性肾损伤早期生物学标志物基础及临床方面的研究进展作一综述.     

诊断早期急性肾损伤的新型标记物的研究进展

背景 急性肾损伤(acute kidney injury,AKI)是外科重症患者术后常见并发症之一,其发病率和死亡率均较高,严重地威胁了患者的生命安全. 目的 为了早期有效识别和诊断外科重症患者术后发生的AKI并及时地提供诊治措施以降低AKI的发病率、改善这类患者的结局.现就这类新型标记物的研究进展作一综述. 内容 主要针对外科重症患者,探讨新型标记物检测在其灵敏性和特异性以及AKI病情评估方面相对于传统检测的优势. 趋向 未来对于外科重症具有高AKI风险因素的患者采用新型标记物外科联合检测将有利于术后AKI的早期诊断和预后评估.     

Inhibition of Na/H exchanger 1 by cariporide alleviates burn-induced multiple organ injury

Background

Severe burns initiate an inflammatory response characterized by the upregulation of proinflammatory cytokine, which contributes to multiple organ injury. Na⁺/H⁺ exchanger 1 (NHE1) plays a significant role in several inflammatory processes. This study was designed to investigate the role of NHE1 in burn-induced inflammation and multiple organ injury.

Materials and methods

Rats were subjected to a 30% total body surface area full-thickness burn. Cariporide was used to assess the function of NHE1 in burn-induced multiple organ injury by biochemical parameters, histologic changes, and inflammatory cytokine production.

Results

We found that NHE1 expression was significantly increased after burn injury. Inhibition of NHE1 by cariporide attenuated burn-induced edema and tissue injury in heart, lung, kidney, and small intestine. Cariporide also inhibited plasma levels of tumor necrosis factor α, interleukin 6, and myeloperoxidase activity.

Conclusions

These results indicate that NHE1 inhibition prevents burn-induced multiple organ injury. The salutary effects afforded by NHE1 inhibition, at least in part, are mediated by attenuating systemic inflammatory response.     

Value of urine IL-8, NGAL and KIM-1 for the early diagnosis of acute kidney injury in patients with ureteroscopic lithotripsy related urosepsis

PurposeTo investigate the clinical value of urine interleukin-18 (IL-8), neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) for the early diagnosis of acute kidney injury (AKI) in patients with ureteroscopic lithotripsy (URL) related urosepsis.MethodsA retrospective study was carried out in 157 patients with urosepsis after URL. The patients were divided into AKI group and non-AKI group according to the Kidigo guideline and urine IL-8, NGAL and KIM-1 levels were detected by enzyme-linked immunosorbent assay at 0, 4, 12, 24 and 48 h after the surgery. Receiver operating characteristic curve (ROC) was used to evaluate the diagnostic value of these three biomarkers for postoperative AKI.ResultsThe level of urine IL-8, NGAL and KIM-1 in AKI group was significantly higher than that in non-AKI group at 4, 12, 24 and 48 h (p < 0.01). The ROC analysis showed the combined detection of urine IL-8, NGAL and KIM-1 at 12 h had a larger area under curve (AUC) than a single marker (0.997, 95% CI: 0.991–0.998), and the sensitivity and specificity were 98.2% and 96.7%, respectively. Pearson correlation analysis showed that the levels of urine NGAL at 4, 12, 24 and 48 h in AKI patients were positively correlated with the levels of urine KIM-1 and IL-18 (p < 0.01).ConclusionAKI could be quickly recognized by the elevated level of urine IL-8, NGAL and KIM-1 in patients with URL-related urosepsis. Combined detection of the three urine biomarkers at 12 h after surgery had a better diagnostic performance, which may be an important reference for the early diagnosis of AKI.     

Urine neutrophil gelatinase-associated lipocalin levels predict acute kidney injury in acute decompensated heart failure patients

Abstract

Background: Acute heart failure (HF) syndromes are frequently complicated with cardiorenal syndromes. The aim of this study was to evaluate the performance of admission neutrophil gelatinase associated lipocalin (NGAL) levels to predict diuretic dose requirement and to predict the occurrence of acute kidney injury (AKI) in patients presenting with acute decompensated HF. Methods: Patients admitted with HF symptoms between December 2010 and October 2011 were prospectively enrolled. Samples were obtained for NGAL and brain natriuretic peptide. Patients were followed up until discharge or for three days, whichever happened first. They were grouped either to have AKI according to “Acute Kidney Injury Network” criteria or not (“no-AKI”). Results: One hundred patients were enrolled. Urine NGAL levels were higher in AKI group (median 31.3 vs. 16.2 ng/mL) (p?<?0.001). Oral furosemide using rates on admission was 60.5% in AKI group, 31.6% in no-AKI group. More AKI developed in patients using less furosemide orally on admission (p?=?0.023). Although the mean furosemide doses were similar on the first day (80?mg), diuretic dose increment was less on the following days in AKI group. Urine NGAL levels with 12?ng/mL cut-off value had sensitivity of 79% and specificity of 67% for predicting AKI. Multiple logistic regression analysis yielded an odds ratio of 10.9 for NGAL levels to predict AKI. Conclusion: Urine NGAL level in decompensated HF patients was not a significant predictor of diuretic dose requirement, but was a good marker for predicting AKI at 12?ng/mL cut-off value.     

Urinary biomarkers may provide prognostic information for subclinical acute kidney injury after cardiac surgery

Objective

This study aimed to determine the biomarker-specific outcome patterns and short-and long-term prognosis of cardiac surgery–asoociated acute kidney injury (AKI) identified by standard criteria and/or urinary kidney biomarkers.

The Role of Na+-H+ Exchanger Isoform 1 in Aldosterone-Induced Glomerulosclerosis in Vivo

Aldosterone is reported to promote fibrosis of multiple organs. Recent studies showed that Na⁺-H⁺ exchanger isoform 1 (NHE1) was involved in mineralocorticoid-induced tissue fibrosis. The present study examined the role of NHE1 in aldosterone-induced glomerulosclerosis in rats. SD male rats were subjected to 5/6 nephrectomy and divided into four groups: rats subjected to sham operation were used as control (SHAM group), 5/6 nephrectomy (SNX group), SNX treated with aldosterone via osmotic mini-pump (ALDO group), and SNX treated with aldosterone plus NHE1 inhibitor 5-(N, N-Dimethyl) amiloride hydrochloride (DMA) (ALDO+DMA group). The rats were sacrificed at the 12th week. We found that aldosterone treatment significantly increased kidney weight/body weight ratio and systolic blood pressure compared with SNX rats. Aldosterone also increased proteinuria and serum creatinine level. The NHE1 antagonist DMA significantly reversed the effect of aldosterone on proteinuria, but had no effect on the aldosterone associated hypertension and the elevation of serum creatinine. The remnant kidney of 5/6 nephrectomized rats exhibited increased glomerulosclerosis score, tubulointerstitial fibrosis, and tubular proteinaceous cast, which were significantly enhanced by aldosterone treatment. DMA treatment significantly reduced aldosterone-associated glomerulosclerosis, but failed to improve aldosterone-induced tubulointerstitial fibrosis and tubular proteinaceous cast. The aldosterone-induced increase in renal TGFβ1 and PCNA was significantly prevented by treatment with DMA. Our data showed that NHE1 inhibitor reduced aldosterone-induced glomerulosclerosis but not hypertension in 5/6 nephrectomized rats. The present study suggested that NHE1 contributed to aldosterone-induced-glomerulosclerosis and could be a potential therapeutic target for chronic kidney disease.     

尿NGAL、NAG及KIM-1联合检测在高龄老年急性肾损伤早期诊断中的价值

目的探讨尿中性粒细胞明胶酶相关脂质运载蛋白(uNGAL)、尿N-乙酰β-D氨基葡萄糖苷酶(uNAG)及尿肾损伤分子-1(uKIM-1)的联合检测老年急性肾损伤中的诊断价值。方法选择2016年6月至2018年6月在泰山疗养院住院的老年患者184例,根据急性肾损伤网络(AKIN)标准为诊断标准,诊断AKI组116例(1期55例、2期39例、3期24例),非AKI组68例,检测并比较各组尿NGAL、NAG、KIM-1水平,用受试者工作特征曲线(ROC)及曲线下面积(AUC)分析3项生物学标志物对AIK的诊断价值。结果①AKI组尿NGAL、NAG、KIM-1明显高于对照组(P<0.05),3期尿NGAL、NAG、KIM-1明显高于2期和1期,2期明显高于1期(P<0.05);②尿NGAL、NAG、KIM-1单独诊断AKI的AUC分别为0.734、0.804、0.705;③3项标志物联合诊断AKI的灵敏度、特异度分别为84.9%、90.7%,高于各单项诊断。结论尿NGAL、NAG、KIM-1是诊断AKI的较好指标,联合诊断对高龄老年急性肾损伤的早期诊断有着更重要的价值。     

Inhibition of Na/H exchanger 1 by cariporide reduces burn-induced intestinal barrier breakdown

Severe burns initiate an inflammatory cascade within the gut, which leads to intestinal mucosal injury. Although Na⁺/H⁺ exchanger 1 (NHE1) is recognised as a pivotal player in several inflammatory processes, its role in burn-induced intestinal injury is relatively unknown. We hypothesised that NHE1 might be involved in the increased intestinal permeability and barrier breakdown after severe burns. Thus, we here investigate whether the inhibition of NHE1 has a protective effect on burn-induced intestinal injury. Mice were subjected to a 30% total body surface area (TBSA) full-thickness steam burn. Cariporide was used to assess the function of NHE1 in mice with burn-induced intestinal injury by fluorescence spectrophotometry, Western blotting and enzyme linked immunosorbent assay (ELISA). We found that severe burn increased intestinal permeability, associated with the up-regulation of NHE1 and raised inflammatory cytokine levels. Mice treated with the NHE1 inhibitor cariporide had significantly attenuated burn-induced intestinal permeability and a reduced inflammatory response. NHE1 inhibition also reduced nuclear factor-κB (NF-κB) activation and attenuated p38 mitogen-activated protein kinase (MAPK) phosphorylation. Our study suggests that NHE1 plays an important role in burn-induced intestinal permeability through the regulation of the inflammatory response. Inhibition of NHE1 may be adopted as a potential therapeutic strategy for attenuating intestinal barrier breakdown.     

Urine neutrophil gelatinase associated lipocalin as an early marker of acute kidney injury in hematopoietic stem cell transplantation patients

Abstract

Acute kidney injury (AKI) is common in hematopoietic stem cell transplantation (HSCT) patients with an incidence of 21–73%. Prevention and early diagnosis reduces the frequency and severity of this complication. Predictive biomarkers are of major importance to timely diagnosis. Neutrophil gelatinase associated lipocalin (NGAL) is a widely investigated novel biomarker for early diagnosis of AKI. However, no study assessed NGAL for AKI diagnosis in HSCT patients. We performed further analyses on gathered data from our recent trial to evaluate the performance of urine NGAL (uNGAL) as an indicator of AKI in 72 allogeneic HSCT patients. AKI diagnosis and severity were assessed using Risk–Injury–Failure–Loss–End-stage renal disease and AKI Network criteria. We assessed uNGAL on days ?6, ?3, +3, +9 and +15. Time-dependant Cox regression analysis revealed a statistically significant relationship between uNGAL and AKI occurrence. (HR?=?1.04 (1.008–1.07), p?=?0.01). There was a relation between uNGAL day?+?9 to baseline ratio and incidence of AKI (unadjusted HR?=?1.047 (1.012–1.083), p?<?0.01). The area under the receiver-operating characteristic curve for day?+?9 to baseline ratio was 0.86 (0.74–0.99, p?<?0.01) and a cut-off value of 2.62 was 85% sensitive and 83% specific in predicting AKI. Our results indicated that increase in uNGAL augmented the risk of AKI and the changes of day +9 uNGAL concentrations from baseline could be of value for predicting AKI in HSCT patients. Additionally uNGAL changes preceded serum Cr raises by nearly 2 days.     

Prediction of acute kidney injury complicated by sepsis with sTREM - 1 and NGAL as early marker

Objective To determine whether triggering receptor expressed on myeloid cells-1 (sTREM - 1) and urinary neutrophil gelatinase - associated lipocalin (NGAL) were early biomarkers of acute kidney injury (AKI) secondary to sepsis. Methods A total of 141 eligible patients were enrolled in this prospective study. Blood and urine samples were collected at different time points as soon as sepsis was diagnosed. The concentrations of serum creatinine (Scr), urine sTREM-1 and NGAL were measured. According to AKI criteria, patients were divided into the AKI group and non - AKI group. Dynamic changes of levels of Scr, urine sTREM-1 and NGAL were observed in two groups. The receiver operating characteristic curves were used to evaluate the early diagnostic value of urine sTREM-1 and NGAL. Results Among 141 septic patients, 44 (31.2%) cases had concomitant AKI. Twenty four hours after sepsis diagnosed, the level of Scr rose to 1.91 times of the baseline [(140.5±13.6) vs (82.6±15.3) μmol/L, P＜0.05], which met the diagnostic criteria of AKI. In the AKI group, urinary concentrations of sTREM-1 and NGAL at 8 h after the diagnosis of sepsis began to rise significantly from baseline [(100.5±17.4) vs (38.9±14.7) ng/L; (144.6±51.9) vs (56.2±43.8) μg/L, both P＜0.05].And at the following time points, urinary concentrations of sTREM - 1 and NGAL were significantly higher than the baseline levels and that of the non-AKI group (all P＜0.05). At 8 h time point, the area under the curve of urine sTREM-1 was 0.877 (95%CI 0.756-0.914), the sensitivity was 89.1% and specificity was 82.0% with a cutoff value of 70 ng/L. At 8 h time point, the area under the curve of urine NGAL was 0.862 (95% CI 0.703-0.958),the sensitivity was 87.4% and specificity was 85.5% with a cutoff value of 90 μg/L. Conclusions Urinary concentrations of sTREM-1 and NGAL at 8 h time point after the diagnosis of sepsis have predictive value for AKI and their diagnostic time is much earlier than that of Scr. Therefore, urinary sTREM-1 and NGAL can be used as early biomarkers of septic AKI.     

Combination of biomarkers for diagnosis of acute kidney injury after cardiopulmonary bypass

Abstract

Novel acute kidney injury (AKI) biomarkers offer promise of earlier diagnosis and risk stratification, but have yet to find widespread clinical application. We measured urinary α and π glutathione S-transferases (α-GST and π-GST), urinary l-type fatty acid-binding protein (l-FABP), urinary neutrophil gelatinase-associated lipocalin (NGAL), urinary hepcidin and serum cystatin c (CysC) before surgery, post-operatively and at 24?h after surgery in 93 high risk patient undergoing cardiopulmonary bypass (CPB) and assessed the ability of these biomarkers alone and in combination to predict RIFLE-R defined AKI in the first 5 post-operative days. Twenty-five patients developed AKI. π-GST (ROCAUC?=?0.75), lower urine Hepcidin:Creatine ratio at 24?h (0.77), greater urine NGAL:Cr ratio post-op (0.73) and greater serum CysC at 24?h (0.72) best predicted AKI. Linear combinations with significant improvement in AUC were: Hepcidin:Cr 24?h?+?post-operative π-GST (AUC?=?0.86, p?=?0.01), Hepcidin:Cr 24?h?+?NGAL:Cr post-op (0.84, p?=?0.03) and CysC 24?h?+?post-operative π-GST (0.83, p?=?0.03), notably these significant biomarkers combinations all involved a tubular injury and a glomerular filtration biomarker. Despite statistical significance in receiver–operator characteristic (ROC) analysis, when assessed by ability to define patients to two groups at high and low risk of AKI, combinations failed to significantly improve classification of risk compared to the best single biomarkers. In an alternative approach using Classification and Regression Tree (CART) analysis a model involving NGAL:Cr measurement post-op followed by Hepcidin:Cr at 24?h was developed which identified high, intermediate and low risk groups for AKI. Regression tree analysis has the potential produce models with greater clinical utility than single combined scores.     

肾损伤标志物对肾移植受者发生DGF的早期预测价值

目的  探讨血中性粒细胞明胶酶相关脂质运载蛋白（NGAL）、尿NGAL、血清胱抑素C（Cys-C）以及血清肌酐（Scr）预测肾移植受者发生肾功能延迟恢复（DGF）的价值。方法  收集159肾移植受者的临床资料及血液、尿液标本,根据是否发生DGF,分为DGF组（42例）和即刻肾功能恢复（IGF）组（117例）。分析两组受者的临床资料,对比两组受者的血NGAL、尿NGAL、Cys-C及Scr变化情况,分析不同指标对DGF的早期预测价值。结果  159例肾移植受者中,42例发生DGF,发生率为26.4%。两组供者年龄、供肾冷缺血时间及补体依赖淋巴细胞毒性试验（CDC）比较,差异有统计学意义（均为P < 0.05）。DGF组血NGAL在术后2周内均高于IGF组（均为P < 0.05）;DGF组Cys-C、Scr、尿NGAL在术后3周内均高于IGF组（均为P < 0.001）。血NGAL、尿NGAL、Cys-C和Scr对肾移植受者发生DGF具有一定预测价值,其中Cys-C预测价值最高,截取值为4.73 mg/L,灵敏度为0.833,特异度为0.812,曲线下面积（AUC）为0.895。结论  Cys-C早期预测肾移植受者发生DGF的价值高于血NGAL、尿NGAL及Scr。     

Luminal osmolarity downregulates gene expression of Na+/H+ exchanger (NHE3) in rat colon mucosa

Water-coupled Na⁺ absorption in the colon is mediated principally by Na⁺/H⁺ exchange (isoforms NHE2 and NHE3). To determine whether luminal ion composition or osmolarity influences NHE expression in colon mucosa, two groups (n = 6 in each) of adult male Sprague-Dawley rats underwent sham laparotomy or loop ileostomy. In these studies, diversion did not markedly alter mRNA levels for NTHE2, NHE3, or Na⁺/K⁺, at 8 or 21 days, indicating that loss of luminal volume does not alter NHE gene expression. To evaluate the effects of specific luminal components, we infused equal volumes of half-normal (154 mOsm) or iso-osmolar (308 mOsm) solutions of saline and mannitol into the diverted colon. All solutions elicited significant (45% to 60%; P <0.05) decreases in mRNA levels for NHE3, with iso-osmolar mannitol eliciting the greatest changes. Decreases in NHE2 and Na⁺/K⁺ mRNA levels were observed following these infusions but were not as marked as the changes for NHE3. These findings suggest that (1) loss of luminal Na⁺ is not, in itself, a signal that regulates NHE expression and (2) infusion of any solute, including Na⁺ itself, provides a signal to downregulate expression of NHE3 in colon mucosa. Supported by the Brigham Surgical Group Foundation and National Institutes of Health Award RO1-DK44571 (D.I.S.).     

Blood cardioplegic protection in profoundly damaged hearts: role of Na+-H+ exchange inhibition during pretreatment or during controlled reperfusion supplementation

BACKGROUND: Inhibition of the Na+/H+ exchanger before ischemia protects against ischemia-reperfusion injury, but use as pretreatment before blood cardioplegic protection or as a supplement to controlled blood cardioplegic reperfusion was not previously tested in jeopardized hearts. METHODS: Control studies tested the safety of glutamate-aspartate-enriched blood cardioplegic solution in 4 Yorkshire-Duroc pigs undergoing 30 minutes of aortic clamping without prior unprotected ischemia. Twenty-four pigs underwent 30 minutes of unprotected normothermic global ischemia to create a jeopardized heart. Six of these hearts received normal blood reperfusion, and the other 18 jeopardized hearts underwent 30 more minutes of aortic clamping with cardioplegic protection. In 12 of these, the Na+/H+ exchanger inhibitor cariporide was used as intravenous pretreatment (n = 6) or added to the cardioplegic reperfusate (n = 6). RESULTS: Complete functional, biochemical, and endothelial recovery occurred after 30 minutes of blood cardioplegic arrest without preceding unprotected ischemia. Thirty minutes of normothermic ischemia and normal blood reperfusion produced 33% mortality and severe left ventricular dysfunction in survivors (preload recruitable stroke work, 23% +/- 6% of baseline levels), with raised creatine kinase MB, conjugated dienes, endothelin-1, myeloperoxidase activity, and extensive myocardial edema. Blood cardioplegia was functionally protective, despite adding 30 more minutes of ischemia; there was no mortality, and left ventricular function improved (preload recruitable stroke work, 58% +/- 21%, p < 0.05 versus normal blood reperfusion), but adverse biochemical and endothelial variables did not change. In contrast, Na+/H+ exchanger inhibition as either pretreatment or added during cardioplegic reperfusion improved myocardial recovery (preload recruitable stroke work, 88% +/- 9% and 80% +/- 7%, respectively, p < 0.05 versus without cariporide) and comparably restored injury variables. CONCLUSIONS: Na+/H+ exchanger blockage as either pretreatment or during blood cardioplegic reperfusion comparably delays functional, biochemical, and endothelial injury in jeopardized hearts.