N-acetylcysteine ameliorates renal microcirculation: studies in rats

Mercapto-responsive polymeric nano-carrier capable of releasing sulfur dioxide

This article reports platform to prepare polymeric nano-carriers capable of releasing SO₂ and hydrophobic payloads upon triggering by mercapto-containing species.

Limb ischemic preconditioning ameliorates renal microcirculation through activation of PI3K/Akt/eNOS signaling pathway after acute kidney injury

Purpose

Contrast-induced acute kidney injury (CI-AKI) resulting from administration of iodinated contrast media (CM) is the third leading cause of hospital-acquired acute kidney injury and is associated with substantial morbidity and mortality. Deteriorated renal microcirculation plays an important role in CI-AKI. Limb ischemic preconditioning (LIPC), where brief and non-injurious ischemia/reperfusion is applied to a limb prior to the administration of the contrast agent, is emerging as a promising strategy for CI-AKI prevention. However, it is not known whether the renal protection of LIPC against CI-AKI is mediated by regulation of renal microcirculation and the molecular mechanisms remain largely unknown.

Methods

In this study, we examined the renal cortical and medullary blood flow in a stable CI-AKI model using 5/6-nephrectomized (NE) rat. The LIPC and sham procedures were performed prior to the injection of CM. Furthermore, we analyzed renal medulla hypoxia using in vivo labeling of hypoxyprobe. Pharmacological inhibitions and western blotting were used to determine the underlying molecular mechanisms.

Results

In this study, we found LIPC significantly ameliorated CM-induced reduction of medullary blood flow and attenuated CM-induced hypoxia. PI3K inhibitor (wortmannin) treatment blocked the regulation of medullary blood flow and the attenuation of hypoxia of LIPC. Phosphorylation of Akt/eNOS was significantly decreased via wortmannin treatment compared with LIPC. Nitric oxide synthase-inhibitor [Nω-nitro-l-arginine methyl ester (L-NAME)] treatment abolished the above effects and decreased phosphorylation of eNOS, but not Akt.

Conclusions

Collectively, the results demonstrate that LIPC ameliorates CM-induced renal vasocontraction and is mediated by activation of PI3K/Akt/eNOS signaling pathway.

Prevention of Contrast Nephropathy in Critically Ill Patients Using Acetylcysteine and Theophylline

Compared with periprocedural hydration alone, acetylcysteine with hydration significantly reduces the risk of contrast nephropathy in patients with chronic renal insufficiency by 50%. For elective contrast procedures, acetylcysteine should be given in a dose of 600 mg twice daily the day before and on the procedure day. For emergency procedures, a high dose intravenous regimen (150 mg/kg in 500 mL normal saline over 30 minutes immediately before contrast followed by 50 mg/kg in 500 mL normal saline over 4h) is effective. Given the low cost and good side-effect profile of acetylcysteine, it would seem prudent to give this drug with intravenous fluids to all critically ill patients scheduled for intravenous or intraarterial contrast procedures. Theophylline in a dose of 200 mg or 2.5 mg/kg IV 30 minutes before contrast may be an effective alternative for emergency procedures. Although its benefit compared with periprocedural hydration alone seems less well established, theophylline is a particularly attractive option for emergency procedures.

A fluorescence and UV/vis absorption dual-signaling probe with aggregation-induced emission characteristics for specific detection of cysteine

Biological thiols with similar structures, such as glutathione (GSH), N-acetyl-l-cysteine (NAC), homocysteine (Hcy) and cysteine (Cys), play important roles in human physiology and are associated with different diseases. Thus, the discrimination of these thiols is a great necessity for various biochemical investigations and the diagnosis of related diseases. Herein, we present a new dual-signaling probe consisting of a typical aggregation induced emission fluorogen of a tetraphenylethylene group and 2,4-dinitrobenzenesulfonyl moiety. The probe can be used to selectively and quantitatively detect Cys over a variety of bio-species, including GSH, NAC and Hcy, from both UV/vis absorption and fluorescence channels. The mechanism study showed that the fluorescence and UV/vis absorption were turned on as the probe undergoes displacement of the 2,4-dinitrobenzenesulfonyl group with Cys, where the UV/vis and fluorescence signals originate from the dinitrophenyl-containing compounds and aggregates of TPE-OH, respectively. In addition, the discrimination of Cys was achieved by more rapid intramolecular displacement of sulfur with the amino group of Cys than NAC, Hcy and GSH. Moreover, the probe shows ignorable cytotoxicity against HepG2 cells, which demonstrates the great potential of the probe in selectively detecting Cys in vivo.

A dual-signaling of fluorescence and UV/vis absorption modes for selective and quantitative detection of cysteine over homocysteine, N-acetyl-l-cysteine and glutathione is developed on the basis of aggregation-induced emission (AIE) effect.

Effects of N-acetylcysteine (NAC) supplementation in resuscitation fluids on renal microcirculatory oxygenation, inflammation, and function in a rat model of endotoxemia. Intensive Care Med Exp. 2016;4:29. [PMID: 27671340 PMCID: PMC5037099 DOI: 10.1186/s40635-016-0106-1]

Background

Modulation of inflammation and oxidative stress appears to limit sepsis-induced damage in experimental models. The kidney is one of the most sensitive organs to injury during septic shock. In this study, we evaluated the effect of N-acetylcysteine (NAC) administration in conjunction with fluid resuscitation on renal oxygenation and function. We hypothesized that reducing inflammation would improve the microcirculatory oxygenation in the kidney and limit the onset of acute kidney injury (AKI).

Methods

Rats were randomized into five groups (n = 8 per group): (1) control group, (2) control + NAC, (3) endotoxemic shock with lipopolysaccharide (LPS) without fluids, (4) LPS + fluid resuscitation, and (5) LPS + fluid resuscitation + NAC (150 mg/kg/h). Fluid resuscitation was initiated at 120 min and maintained at fixed volume for 2 h with hydroxyethyl starch (HES 130/0.4) dissolved in acetate-balanced Ringer’s solution (Volulyte) with or without supplementation with NAC (150 mg/kg/h). Oxygen tension in the renal cortex (CμPO₂), outer medulla (MμPO₂), and renal vein was measured using phosphorimetry. Biomarkers of renal injury, inflammation, and oxidative stress were assessed in kidney tissues.

Results

Fluid resuscitation significantly improved the systemic and renal macrohemodynamic parameters after LPS. However, the addition of NAC further improved cortical renal oxygenation, oxygen delivery, and oxygen consumption (p < 0.05). NAC supplementation dampened the accumulation of NGAL or L-FABP, hyaluronic acid, and nitric oxide in kidney tissue (p < 0.01).

Conclusion

The addition of NAC to fluid resuscitation may improve renal oxygenation and attenuate microvascular dysfunction and AKI. Decreases in renal NO and hyaluronic acid levels may be involved in this beneficial effect. A therapeutic strategy combining initial fluid resuscitation with antioxidant therapies may prevent sepsis-induced AKI.

Pretreatment with endothelium-derived nitric oxide synthesis modulators on gastrointestinal microcirculation during NOTES: an experimental study

BACKGROUND AND STUDY AIMS

On-demand endoscopic insufflation during natural orifice transluminal endoscopic surgery (NOTES) adversely affects microcirculatory blood flow (MBF), even with low mean intra-abdominal pressure, suggesting that shear stress caused by time-varying flow fluctuations has a great impact on microcirculation. As shear stress is inversely related to vascular diameter, nitric oxide (NO) production acts as a brake to vasoconstriction.

OBJECTIVE

To assess whether pretreatment by NO synthesis modulators protects gastrointestinal MBF during transgastric peritoneoscopy.

METHODS

Fourteen pigs submitted to cholecystectomy by endoscope CO₂ insufflation for 60 min were randomized into 2 groups: (1) 150 mg/kg of N-acetyl cysteine (NAC, n = 7) and (2) 4 ml/kg of hypertonic saline 7.5 % (HS, n = 7), and compared to a non-treated NOTES group (n = 7). Five animals made up a sham group. Colored microspheres were used to assess changes in MBF.

RESULTS

The average level of intra-abdominal pressure was similar in all groups (9 mmHg). In NOTES group microcirculation decrease compared with baseline was greater in renal cortex, mesocolon, and mesentery (41, 42, 44 %, respectively, p < 0.01) than in renal medulla, colon, and small bowel (29, 32, 34, respectively, p < 0.05). NAC avoided the peritoneoscopy effect on renal medulla and cortex (4 and 14 % decrease, respectively) and reduced the impact on colon and small bowel (20 % decrease). HS eliminated MBF changes in colon and small bowel (14 % decrease) and modulated MBF in renal medulla and cortex (19 % decrease). Neither treatment influenced mesentery MBF decrease.

CONCLUSIONS

Both pretreatments can effectively attenuate peritoneoscopy-induced deleterious effects on gastrointestinal MBF.

Effect of N-acetylcysteine pretreatment of deceased organ donors on renal allograft function: a randomized controlled trial

BACKGROUND

Antioxidant donor pretreatment is one of the pharmacologic strategy proposed to prevent renal ischemia-reperfusion injuries and delayed graft function (DGF). The aim of the study was to investigate whether a donor pretreatment with N-acetylcysteine (NAC) reduces the incidence of DGF in adult human kidney transplant recipients.

METHODS

In this randomized, open-label, monocenter trial, 160 deceased heart-beating donors were allowed to perform 236 renal transplantations from September 2005 to December 2010. Donors were randomized to receive, in a single-blind controlled fashion, 600 mg of intravenous NAC 1 hr before and 2 hr after cerebral angiography performed to confirm brain death. Primary endpoint was DGF defined by the need for at least one dialysis session within the first week or a serum creatinine level greater than 200 μmol/L at day 7 after kidney transplantation.

RESULTS

The incidence of DGF was similar between donors pretreated with or without NAC (39/118; 33% vs. 30/118; 25.4%; P = 0.19). Requirement for at least one dialysis session was not different between the NAC and No NAC groups (17/118; 14.4% vs. 14/118; 11.8%, P = 0.56). The two groups had comparable serum creatinine levels, estimated glomerular filtration rates, and daily urine output at days 1, 7, 15, and 30 after kidney transplantation as well as at hospital discharge. No difference in recipient mortality nor in 1-year kidney graft survival was observed.

CONCLUSION

Donor pretreatment with NAC does not improve delayed graft function after kidney transplantation.

Epac-Rap signaling reduces oxidative stress in the tubular epithelium

Activation of Rap1 by exchange protein activated by cAMP (Epac) promotes cell adhesion and actin cytoskeletal polarization. Pharmacologic activation of Epac-Rap signaling by the Epac-selective cAMP analog 8-pCPT-2'-O-Me-cAMP during ischemia-reperfusion (IR) injury reduces renal failure and application of 8-pCPT-2'-O-Me-cAMP promotes renal cell survival during exposure to the nephrotoxicant cisplatin. Here, we found that activation of Epac by 8-pCPT-2'-O-Me-cAMP reduced production of reactive oxygen species during reoxygenation after hypoxia by decreasing mitochondrial superoxide production. Epac activation prevented disruption of tubular morphology during diethyl maleate-induced oxidative stress in an organotypic three-dimensional culture assay. In vivo renal targeting of 8-pCPT-2'-O-Me-cAMP to proximal tubules using a kidney-selective drug carrier approach resulted in prolonged activation of Rap1 compared with nonconjugated 8-pCPT-2'-O-Me-cAMP. Activation of Epac reduced antioxidant signaling during IR injury and prevented tubular epithelial injury, apoptosis, and renal failure. Our data suggest that Epac1 decreases reactive oxygen species production by preventing mitochondrial superoxide formation during IR injury, thus limiting the degree of oxidative stress. These findings indicate a new role for activation of Epac as a therapeutic application in renal injury associated with oxidative stress.

The oxidative stress induced in vivo by Shiga toxin-2 contributes to the pathogenicity of haemolytic uraemic syndrome

Typical haemolytic uraemic syndrome (HUS) is caused by Shiga toxin (Stx)-producing Escherichia coli infections and is characterized by thrombotic microangiopathy that leads to haemolytic anaemia, thrombocytopenia and acute renal failure. Renal or neurological sequelae are consequences of irreversible tissue damage during the acute phase. Stx toxicity and the acute inflammatory response raised by the host determine the development of HUS. At present there is no specific therapy to control Stx damage. The pathogenic role of reactive oxygen species (ROS) on endothelial injury has been largely documented. In this study, we investigated the in-vivo effects of Stx on the oxidative balance and its contribution to the development of HUS in mice. In addition, we analysed the effect of anti-oxidant agents as therapeutic tools to counteract Stx toxicity. We demonstrated that Stx induced an oxidative imbalance, evidenced by renal glutathione depletion and increased lipid membrane peroxidation. The increased ROS production by neutrophils may be one of the major sources of oxidative stress during Stx intoxication. All these parameters were ameliorated by anti-oxidants reducing platelet activation, renal damage and increasing survival. To conclude, Stx generates a pro-oxidative state that contributes to kidney failure, and exogenous anti-oxidants could be beneficial to counteract this pathogenic pathway.

Radiographic contrast-media-induced acute kidney injury: pathophysiology and prophylactic strategies

Contrast-induced acute kidney injury (CI-AKI) is one of the most widely discussed and debated topics in cardiovascular medicine. With increasing number of contrast-media- (CM-) enhanced imaging studies being performed and growing octogenarian population with significant comorbidities, incidence of CI-AKI remains high. In this review, pathophysiology of CI-AKI, its relationship with different types of CM, role of serum and urinary biomarkers for diagnosing CI-AKI, and various prophylactic strategies used for nephroprotection against CI-AKI are discussed in detail.

Intravenous N-acetylcysteine for prevention of contrast-induced nephropathy: a meta-analysis of randomized, controlled trials

Background

Contrast-induced nephropathy (CIN) is one of the common causes of acute renal insufficiency after contrast procedures. Whether intravenous N-acetylcysteine (NAC) is beneficial for the prevention of contrast-induced nephropathy is uncertain. In this meta-analysis of randomized controlled trials, we aimed to assess the efficacy of intravenous NAC for preventing CIN after administration of intravenous contrast media.

Study Design

Relevant studies published up to September 2012 that investigated the efficacy of intravenous N-acetylcysteine for preventing CIN were collected from MEDLINE, OVID, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials, and the conference proceedings from major cardiology and nephrology meetings. The primary outcome was CIN. Secondary outcomes included renal failure requiring dialysis, mortality, and length of hospitalization. Data were combined using random-effects models with the performance of standard tests to assess for heterogeneity and publication bias. Meta-regression analyses were also performed.

Results

Ten trials involving 1916 patients met our inclusion criteria. Trials varied in patient demographic characteristics, inclusion criteria, dosing regimens, and trial quality. The summary risk ratio for contrast-induced nephropathy was 0.68 (95% CI, 0.46 to 1.02), a nonsignificant trend towards benefit in patients treated with intravenous NAC. There was evidence of significant heterogeneity in NAC effect across studies (Q = 17.42, P = 0.04; I² = 48%). Meta-regression revealed no significant relation between the relative risk of CIN and identified differences in participant or study characteristics.

Conclusion

This meta-analysis showed that research on intravenous N-acetylcysteine and the incidence of CIN is too inconsistent at present to warrant a conclusion on efficacy. A large, well designed trial that incorporates the evaluation of clinically relevant outcomes in participants with different underlying risks of CIN is required to more adequately assess the role for intravenous NAC in CIN prevention.

Effect of N-acetylcysteine on residual renal function in chronic haemodialysis patients treated with high-flux synthetic dialysis membranes: a pilot study

Background. Preservation of residual renal function in chronic dialysis patients has proven to be a major predictor of survival. The aim of the present study was to investigate an ability of the combined use of N-acetylcysteine and high-flux biocompatible haemodialysis membranes to improve residual renal function in haemodialysis patients. Patients and Methods. Chronic haemodialysis patients with a residual urine output of at least 100 mL/24 h were administered oral an N-acetylcysteine 1200 mg twice daily for 2 weeks. Treatment group included patients treated with dialysers using high-flux synthetic biocompatible membranes. Control group included patients treated with dialysers using low-flux semisyntetic triacetate haemodialysis membranes. Results. Eighteen patients participated in the study. The residual glomerular filtration rate showed a nonsignificant trend for increase in both groups. The magnitude of GFR improvement after N-acetylcysteine administration was less pronounced in the group treated with high-flux biocompatible membranes: +0.17 ± 0.56 mL/min/1.73 m(2) in treatment group and +0.65 ± 0.53 mL/min/1.73 m(2) in control group (P < 0.05). Conclusion. In this study of favorable effect of N-acetylcysteine on residual renal function in chronic haemodialysis patients may be less pronounced when using high-flux biocompatible, rather than low-flux semisyntetic, HD membranes.

Prevention of contrast-induced nephropathy: A randomized controlled trial of sodium bicarbonate and N-acetylcysteine

BACKGROUND

Contrast-induced nephropathy (CIN) continues to be a common cause of acute renal failure in high-risk patients undergoing radiocontrast studies. However, there is still a lack of consensus regarding the most effective measures to prevent CIN.

METHODS

ONE HUNDRED EIGHTEEN PATIENTS WITH DIABETES MELLITUS AND/OR RENAL INSUFFICIENCY, SCHEDULED FOR CORONARY ANGIOGRAPHY OR INTERVENTION, WERE RANDOMLY ASSIGNED TO ONE OF FOUR TREATMENT GROUPS: intravenous (IV) 0.9% NaCl alone, IV 0.9% NaCl plus N-acetylcysteine (NAC), IV 0.9% sodium bicarbonate (NaHCO(3)) alone or IV 0.9% NaHCO(3) plus NAC. All patients received IV hydration as a preprocedure bolus and as maintenance. Iso-osmolar contrast was used in all patients. CIN was defined as an increase of greater than 25% in the serum creatinine concentration from baseline to 72 h.

RESULTS

The overall incidence of CIN was 6%. There was no statistically significant difference in the incidence of CIN among the groups. There was a CIN incidence of 7% in the NaCl only group, 5% in the NaCl/NAC group, 11% in the NaHCO(3) only group and 4% in the NaHCO(3)/NAC group (P=0.86). The maximum increase in serum creatinine was 14.14±12.38 μmol/L in the NaHCO(3) group, 10.60±29.14 μmol/L in the NaCl only group, 9.72±13.26 μmol/L in the NaCl/NAC group and 0.177±15.91 μmol/L for the NaHCO(3)/NAC group (P=0.0792).

CONCLUSION

CIN in high-risk patients may be effectively minimized solely through the use of an aggressive hydration protocol and an iso-osmolar contrast agent. The addition of NaHCO(3) and/or NAC did not have an effect on the incidence of CIN.

The antihypertensive effect of cysteine

Hypertension is a leading cause of morbidity and mortality worldwide. Individuals with hypertension are at an increased risk for stroke, heart disease and kidney failure. Essential hypertension results from a combination of genetic and lifestyle factors. One such lifestyle factor is diet, and its role in the control of blood pressure has come under much scrutiny. Just as increased salt and sugar are known to elevate blood pressure, other dietary factors may have antihypertensive effects. Studies including the Optimal Macronutrient Intake to Prevent Heart Disease (OmniHeart) study, Multiple Risk Factor Intervention Trial (MRFIT), International Study of Salt and Blood Pressure (INTERSALT) and Dietary Approaches to Stop Hypertension (DASH) study have demonstrated an inverse relationship between dietary protein and blood pressure. One component of dietary protein that may partially account for its antihypertensive effect is the nonessential amino acid cysteine. Studies in hypertensive humans and animal models of hypertension have shown that N-acetylcysteine, a stable cysteine analogue, lowers blood pressure, which substantiates this idea. Cysteine may exert its antihypertensive effects directly or through its storage form, glutathione, by decreasing oxidative stress, improving insulin resistance and glucose metabolism, lowering advanced glycation end products, and modulating levels of nitric oxide and other vasoactive molecules. Therefore, adopting a balanced diet containing cysteine-rich proteins may be a beneficial lifestyle choice for individuals with hypertension. An example of such a diet is the DASH diet, which is low in salt and saturated fat; includes whole grains, poultry, fish and nuts; and is rich in vegetables, fruits and low-fat dairy products.

Effect of N-acetylcysteine and fructose-1,6-bisphosphate in the treatment of experimental sepsis

Sepsis is a syndrome caused by uncontrolled systemic inflammatory response of the individual, which represents a serious epidemiological problem worldwide. The aim of this study was to investigate the effect of N-acetylcysteine (NAC) and fructose-1,6-bisphosphate (FBP) in the treatment of experimental sepsis. We used rats that were divided into five experimental groups: normal control (not induced), septic control (induced using a capsule with non sterile fecal content and Escherichia coli), treated with FBP (500 mg/kg i.p.), treated with NAC (150 mg/kg i.p.), and treated with the combination of FBP with NAC. In the group treated with NAC, 16.68% of the mice survived, the FBP reduced the mortality of mice during the acute stage of the disease and increased the animals' survival time in 33.34%, and the combination of drugs had no effect. Our results show that NAC prevented the mortality of animals after septic induction. These data confirm the validity of the use of NAC in the treatment of sepsis. Our data also show that the synergistic action with FBP does not improve the picture.

N-acetylcysteine may improve residual renal function in hemodialysis patients: a pilot study

Clinical outcomes in chronic dialysis patients are highly dependent on preservation of residual renal function (RRF). N-acetylcysteine (NAC) may have a positive effect on renal function in the setting of nephrotoxic contrast media administration. In our recent study, we showed that NAC may improve RRF in peritoneal dialysis patients. The aim of the present study was to investigate the effect of NAC on RRF in patients treated with chronic hemodialysis. Prevalent chronic hemodialysis patients with a residual urine output of at least 100 mL/24 hours were included. The patients were administered oral NAC 1200 mg twice daily for 2 weeks. Residual renal function was assessed at baseline and at the end of treatment using a midweek interdialytic urine collection for measurement of urine output and calculation of residual renal Kt/V and glomerular filtration rate (GFR). Residual GFR was measured as the mean of urea and creatinine residual renal clearance. Each patient served as his own control. Twenty patients were prospectively enrolled in the study. Administration of NAC 1200 mg twice daily for 2 weeks resulted in significant improvement in RRF: urine volume increased from 320 ± 199 to 430 ± 232 mL/24 hours (P < 0.01), residual renal Kt/V increased from 0.19 ± 0.12 to 0.29 ± 0.14 (P < 0.01), and residual GFR increased from 1.6 ± 1.6 to 2.4 ± 2.3 mL/minute/1.73 m(2) (P < 0.01). N-acetylcysteine may improve RRF in patients treated with chronic hemodialysis.

N-acetylcysteine attenuates dimethylnitrosamine induced oxidative stress in rats

Oxidative stress has been implicated in the pathogenesis and progression of various hepatic disorders and hence screening for a good hepatoprotective and antioxidant agent is the need of the hour. The present study was aimed to investigate the hepatoprotective and antioxidant property of N-acetylcysteine (NAC) against dimethylnitrosamine (DMN) induced oxidative stress and hepatocellular damage in male Wistar albino rats. Administration of single dose of DMN (5mg/kg b.w.; i.p.) resulted in significant elevation in the levels of serum aspartate transaminase and alanine transaminase, indicating hepatocellular damage. Oxidative stress induced by DMN treatment was confirmed by an elevation in the status of lipid peroxidation (LPO) and reduction in the activities of enzymic antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase and in the levels of non-enzymic antioxidants, reduced glutathione, vitamin-C and vitamin-E in the liver tissue. DMN induced oxidative stress and hepatocellular membrane instability was further substantiated by a decline in the status of the membrane bound ATPases in the liver tissue. Post-treatment with NAC (50mg/kg b.w.; p.o.) for 7days effectively protected against the DMN induced insult to liver by preventing the elevation in the status of the serum marker enzymes and LPO, and restoring the activities of both the enzymic and non-enzymic antioxidants and membrane bound ATPases towards normalcy. These results demonstrate that NAC acts as a good hepatoprotective and antioxidant agent in attenuating DMN induced oxidative stress and hepatocellular damage.

N-acetylcysteine improves residual renal function in peritoneal dialysis patients: a pilot study

BACKGROUND

Preservation of peritoneal membrane function and residual renal function is important for the optimal care of peritoneal dialysis patients. N-Acetylcysteine may ameliorate oxidative stress, which is thought to be involved in peritoneal membrane dysfunction. In addition, N-acetylcysteine may have a positive effect on renal function in the setting of nephrotoxic contrast media administration. The aim of this study was to investigate the effect of N-acetylcysteine on peritoneal and residual renal function in peritoneal dialysis patients.

METHODS

Ten prevalent peritoneal dialysis patients were administered oral N-acetylcysteine 1200 mg twice daily for 4 weeks. At baseline and at the end of treatment, peritoneal membrane function and residual renal function were assessed using a 4.25% dextrose peritoneal equilibration test and 24-hour dialysate and urine collection for calculation of peritoneal and residual renal Kt/V and mean urea and creatinine residual renal clearance.

RESULTS

No significant changes were demonstrated in peritoneal membrane function, including dialysate-to-plasma creatinine ratio, sodium sieving, and net ultrafiltration. Residual renal function improved significantly: urine volume increased from 633 ± 426 to 925 ± 552 mL/24 hours (p = 0.022), residual renal Kt/V increased from 0.56 ± 0.41 to 0.75 ± 0.47 (p = 0.037), and mean residual urea and creatinine clearance increased from 4.96 ± 3.96 to 5.95 ± 4.08 mL/min/1.73 m(2) (p = 0.059).

CONCLUSIONS

N-acetylcysteine may improve residual renal function in patients treated with peritoneal dialysis.

Reactive oxygen species and the pathogenesis of radiocontrast-induced nephropathy. Invest Radiol. 2010;45:188-195. [PMID: 20195159 DOI: 10.1097/rli.0b013e3181d2eed8]

Experimental findings in vitro and in vivo illustrate enhanced hypoxia and the formation of reactive oxygen species (ROS) within the kidney following the administration of iodinated contrast media, which may play a role in the development of contrast media-induced nephropathy. Clinical studies indeed support this possibility, suggesting a protective effect of ROS scavenging or reduced ROS formation with the administration of N-acetyl cysteine and bicarbonate infusion, respectively. Furthermore, most risk factors, predisposing to contrast-induced nephropathy are prone to enhanced renal parenchymal hypoxia and ROS formation. In this review, the association of renal hypoxia and ROS-mediated injury is outlined. Generated during contrast-induced renal parenchymal hypoxia, ROS may exert direct tubular and vascular endothelial injury and might further intensify renal parenchymal hypoxia by virtue of endothelial dysfunction and dysregulation of tubular transport. Preventive strategies conceivably should include inhibition of ROS generation or ROS scavenging.

Prevention of acute kidney injury and protection of renal function in the intensive care unit. Expert opinion of the Working Group for Nephrology, ESICM

BACKGROUND

Acute renal failure on the intensive care unit is associated with significant mortality and morbidity.

OBJECTIVES

To determine recommendations for the prevention of acute kidney injury (AKI), focusing on the role of potential preventative maneuvers including volume expansion, diuretics, use of inotropes, vasopressors/vasodilators, hormonal interventions, nutrition, and extracorporeal techniques.

METHOD

A systematic search of the literature was performed for studies using these potential protective agents in adult patients at risk for acute renal failure/kidney injury between 1966 and 2009. The following clinical conditions were considered: major surgery, critical illness, sepsis, shock, and use of potentially nephrotoxic drugs and radiocontrast media. Where possible the following endpoints were extracted: creatinine clearance, glomerular filtration rate, increase in serum creatinine, urine output, and markers of tubular injury. Clinical endpoints included the need for renal replacement therapy, length of stay, and mortality. Studies are graded according to the international Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) group system.

CONCLUSIONS AND RECOMMENDATIONS

Several measures are recommended, though none carries grade 1A. We recommend prompt resuscitation of the circulation with special attention to providing adequate hydration whilst avoiding high-molecular-weight hydroxy-ethyl starch (HES) preparations, maintaining adequate blood pressure using vasopressors in vasodilatory shock. We suggest specific vasodilators [corrected] under strict hemodynamic control, sodium bicarbonate for emergency procedures administering contrast media, and periprocedural hemofiltration in severe chronic renal insufficiency undergoing coronary intervention.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s00134-009-1678-y) contains supplementary material, which is available to authorized users.

N-acetylcysteine does not prevent hepatorenal ischaemia-reperfusion injury in patients undergoing orthotopic liver transplantation

BACKGROUND

Glutathione (GSH) acts as a free radical scavenger that may be helpful in preventing reperfusion injury. N-acetylcysteine (NAC) replenishes GSH stores. The aims of this study were to evaluate the efficacy of NAC in improving liver graft performance and reducing the incidence of post-operative acute kidney injury (AKI).

METHODS

Our study was a randomized, double-blind, placebo-controlled trial of 100 patients; 50 received placebo and 50 received a loading dose of 140 mg/kg of intravenous (IV) NAC over 1 h followed by 70 mg/kg IV repeated every 4 h for a total of 12 doses. Both groups were followed up for 1 year post-orthotopic liver transplant (OLT). We recorded liver function tests, renal function tests, graft survival, patient survival, plasma GSH and duration of hospital and ICU stay. In addition to serum creatinine (SCr) levels, we analysed cystatin C and beta-trace as independent measures of glomerular filtration. All clinical data were recorded daily for the first week after the surgery, then on Days 14, 21, 30, 90 and 180 and at the end of the first year.

RESULTS

IV NAC did not affect survival, graft function or risk of AKI. However, GSH levels were highly variable with only 50% of patients receiving NAC exhibiting increased levels and fewer patients developed AKI when GSH levels were increased. Additional risk factors for AKI in the post-transplant period were female gender (P = 0.05), increased baseline serum bilirubin (P = 0.004) and increased baseline SCr levels (P = 0.02).

CONCLUSIONS

IV NAC was not effective in reducing renal or hepatic injury in the setting of liver transplantation. The dose and duration of NAC used, though higher than most renal protection studies, may have been ineffective for raising GSH levels in some patients.

N-acetylcysteine infusion reduces the resistance index of renal artery in the early stage of systemic sclerosis

AIM

To evaluate resistance index (RI) changes in renal artery after N-acetylcysteine infusion in patients with systemic sclerosis.

METHODS

In an open-label study 40 patients with systemic sclerosis (SSc) were treated with N-acetylcysteine (NAC) iv infusion over 5 consecutive hours, at a dose of 0.015 g x kg(-1) x h(-1). Renal haemodynamic effects were evaluated by color Doppler examination before and after NAC infusion.

RESULTS

NAC infusion significantly reduced RI in a group of sclerodermic patients with early/active capillaroscopic pattern, modified Rodnan Total Skin Score (mRTSS) <14 and mild-moderate score to the vascular domain of Medsger Scleroderma Disease Severity Scale (DSS). RI increased after NAC infusion in patients with late capillaroscopic pattern, mTRSS>14 and severe-end stage score to the vascular domain of DSS. In patients with reduction of RI after NAC infusion, diffusion capacity for carbon monoxide mean value was significantly higher than in those patients with an increase of RI. No significant differences in renal blood flow were found between patients with different subsets of SSc.

CONCLUSION

In patients with low disease severity NAC ameliorates vascular renal function.

Acetylcysteine and non-ionic isosmolar contrast-induced nephropathy--a randomized controlled study

INTRODUCTION

Intravenous administration of saline and non-ionic isosmolar contrast media significantly reduces the incidence of contrast-induced nephropathy, one of the most common causes of acute renal failure. Results with oral N-acetylcysteine are conflicting. The aim of our study was to evaluate the prophylactic role of N-acetylcysteine in patients with stable chronic renal failure undergoing coronary and/or peripheral angiography and/or angioplasty.

METHODS

We randomized 200 elective, consecutive patients (mean age 74.9 +/- 7.3 years; 65% male, 25% diabetics) with basal creatinine clearance <or=55 ml/min to receive oral N-acetylcysteine (600 mg bid the day before and the day of the procedure plus saline i.v. 0.9% 1 ml/kg/h 12-24 h before and 24 h after the procedure, n = 99) or placebo and saline at the same time intervals, n = 101. The contrast medium was non-ionic isosmolar (Iodixanol, Visipaque Amersham Health). Contrast-induced nephropathy was defined as an increase in serum creatinine >0.5 mg/dl or >25% within 3 days after the procedure. Serum creatinine was measured at baseline, 24, 48 and 72 h after the procedure.

RESULTS

Contrast-induced nephropathy was 8/99 (8.1%) in the N-acetylcysteine group versus 6/101 (5.9%) in the placebo group, P = 0.6. No difference was noted in high-risk subgroups such as diabetics (4/25 versus 2/25 P = 0.4) and those with serum creatinine clearance <42.3 ml/min (5/54 versus 4/48; P = 0.9).

CONCLUSION

In our experience, N-acetylcysteine did not prevent contrast-induced nephropathy in patients receiving isosmolar (iodixanol) contrast media and adequate hydration.

N-acetylcysteine and fenoldopam protect the renal function of patients with chronic renal insufficiency undergoing cardiac surgery

OBJECTIVE

To determine whether fenoldopam and N-acetylcysteine prevent renal deterioration and improve hospital outcome for patients with chronic renal insufficiency undergoing cardiac surgery.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled trial.

SETTING

A community hospital that is a cardiac referral center.

PATIENTS

Seventy-nine adult patients with chronic renal insufficiency (creatinine clearance < or = 40 mL/min) who underwent cardiac surgery.

INTERVENTIONS

Group 1 received intravenous fenoldopam 0.1 microg/kg/min started at surgical induction and continued for 48 hrs. Group 2 received N-acetylcysteine 600 mg orally twice a day, from preoperative day 1 to postoperative day 1. Group 3 received both fenoldopam and N-acetylcysteine, and group 4 patients served as controls.

MEASUREMENTS AND MAIN RESULTS

Using multiple comparisons (analysis of variance) with change scores, and statistically adjusting for group differences in aortic cross-clamp time, use of intraoperative aprotinin, and preoperative use of statin, we found that the change in creatinine clearance from preoperative to postoperative day 3 was statistically less for group 1 (-1.47 mL/min +/- 2.06 SE, p = .0286) and for group 2 (-0.67 mL/min +/- 2.11 SE, p = .0198) and less but not quite significant for group 3 (-3.08 mL/min +/- 1.95 SE, p = .0891) compared with controls (-8.15 mL/min +/- 2.18 SE). Furthermore, the adjusted weight gain on postoperative day 3 was 5.55 kg +/- 1.00 SE (p = .0988) for group 1, 5.06 kg +/- 1.06 SE (p = .0631) for group 2, and 5.14 kg +/- .91 SE (p = .0445) for group 3 compared with 8.03 kg +/- 1.07 SE for group 4. However, there was no decrease in length of critical care or hospital stay or hospital costs. Finally, fenoldopam contributed to perioperative hypotension.

CONCLUSIONS

Perioperative fenoldopam and N-acetylcysteine abrogate the early postoperative decline in renal function of patients who have chronic renal insufficiency, although these agents do not affect other parameters of cardiac surgical outcome.

Medical therapy of acute kidney injury

Pharmacologic interventions for the prevention and therapy of acute kidney injury (AKI) can be roughly divided into 2 main strategies: Optimising renal perfusion and modulation of intrarenal pathophysiological mechanisms, i.e. formation of free oxygen radicals, inflammation, tubular cast formation and renal (tubular) regeneration. Improvement of impaired renal perfusion can be achieved by optimising systemic haemodynamics by volume expansion and the appropriate use of inotropes and/or vasopressors. Up to now prospective randomised controlled trials on selective renal vasodilatation have turned out rather unsuccessful, with the exception of the adenosine antagonist theophylline, in certain indications like drug-induced renal failure or contrast nephropathy. Studies in humans on pharmacological interventions interfering with intrarenal pathophysiological mechanisms of AKI are also sparse. Investigated compounds comprise N-acetyl-cysteine, mannitol and antioxidants like selenium or vitamin C. The results are heterogeneous and a significant beneficial effect of either substance could not yet be convincingly demonstrated.

Renal parenchymal hypoxia, hypoxia adaptation, and the pathogenesis of radiocontrast nephropathy

BACKGROUND AND OBJECTIVES

Renal parenchymal Po(2) declines after the administration of iodinated radiocontrast agents, reaching critically low levels of approximately 10 mmHg in medullary structures.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this review, the causes of renal parenchymal hypoxia and its potential role in the pathogenesis of contrast nephropathy are appraised.

RESULTS

Commonly associated predisposing factors are associated with a propensity to enhance renal hypoxia. Indeed, animal models of radiocontrast nephropathy require the induction of such predisposing factors, mimicking clinical scenarios that lead to contrast nephropathy in high-risk individuals. In these models, in association with medullary hypoxic damage, a transient local cellular hypoxia response is noted, initiated at least in part by hypoxia-inducible factors. Some predisposing conditions that are distinguished by chronically aggravated medullary hypoxia, such as tubulointerstitial disease and diabetes, are characterized by a priori upregulation of hypoxia-inducible factors, which seems to confer tolerance against radiocontrast-related hypoxic tubular damage. Renal dysfunction under such circumstances likely reflects to some extent altered intrarenal hemodynamics, rather than acute tubular injury.

CONCLUSIONS

Real-time, noninvasive novel methods may help to differentiate between evolving tubular damage and altered hemodynamics and in the design of appropriate preventive interventions.

N-acetylcysteine in the prevention of contrast-induced nephropathy

BACKGROUND AND OBJECTIVES

Contrast-induced nephropathy (CIN) is a common clinical problem that is growing in importance as an increasing number of tests and procedures that utilize contrast media are performed.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The biological and pharmacological properties of n-acetylcysteine (NAC) are reviewed, as well as the current literature relevant to the ability of NAC to prevent CIN.

RESULTS

After publication of a seminal study by Tepel et al. in 2000, there has been a surge in interest regarding the ability of NAC to reduce the risk for CIN. Since then a large number of studies, mostly with relatively small sample sizes, have been published.

CONCLUSIONS

The results have been remarkably varied with some studies finding great efficacy with NAC but most finding no significant benefit.

Contrast-induced nephropathy

Interventional radiological procedures involving anaesthesia are generally increasing. Contrast-induced nephropathy (CIN), usually defined as an increase in serum creatinine of 44 micromol litre(-1) (0.5 mg dl(-1)) or a 25% increase from the baseline value 48 h after intravascular injection of contrast media, is a common and potentially serious complication of the use of iodinated contrast media in patients at risk of acute renal injury. It is an important cause of hospital-acquired renal failure, may be a difficult differential diagnosis and the incidence does not appear to have changed over the last few decades. In the general population, the incidence of CIN is estimated to be 1-2%. However, the risk for developing CIN may be as high as 50% in some patient subgroups, such as those with diabetes mellitus and pre-existing renal impairment. The impact of CIN on clinical outcomes has been evaluated most extensively in patients undergoing percutaneous coronary intervention where it is associated with increased mortality both in hospital and at 1 yr. As treatment is limited to supportive measures while awaiting the resolution of the renal impairment, emphasis needs to be directed at prevention.

Pathophysiology of contrast-induced nephropathy

Contrast-induced nephropathy (CIN) is the third leading cause of acute kidney injury in hospitalized patients and is associated with significant patient morbidity. The pathogenesis of CIN is complex and not fully understood, but iodinated contrast agents induce intense and prolonged vasoconstriction at the corticomedullary junction of the kidney. Moreover, high-osmolar dyes directly impair the autoregulatory capacity of the kidney through a loss of nitric oxide production. These effects, coupled with direct tubular toxicity of contrast media, lead to overt acute tubular necrosis and the syndrome of CIN.

Allopurinol and enalapril failed to conserve urinary NOx and sodium in ischemic acute renal failure in spontaneously hypertensive rats

BACKGROUND

Ischemia-reperfusion-induced acute renal failure (ARF) is associated with a high mortality in patients with hypertension and with an unfavorable outcome of kidney transplants from marginal donors.

AIM

The influence of allopurinol and enalapril on urinary nitrate/nitrite (UNOx), glomerular filtration rate, plasma and urinary sodium, and hemodynamic parameters was examined in spontaneously hypertensive rats (SHR) with ARF.

METHODS

ARF was induced by right-kidney removal and clamping the left renal artery for 40 min in 50 male 26-week-old SHR weighing 300 +/- 23 g. The rats were randomly allocated to five groups: (1) sham operated; (2) ARF; (3) ARF after pretreatment with 40 mg/kg allopurinol; (4) ARF after pretreatment with 40 mg/kg enalapril, and (5) ARF after pretreatment with 40 mg/kg allopurinol and 40 mg/kg enalapril. Creatinine clearance, UNOx (Griess reaction), cardiac output (dye dilution technique), mean arterial blood pressure, and renal blood flow were measured 24 h after reperfusion. Total vascular resistance and renal vascular resistance were calculated and compared between the groups.

RESULTS

A nonsignificant decrease was found in both daily UNOx excretion and creatinine clearance when pretreated ARF groups and the ARF group without pretreatment were compared (p > 0.05). Significantly lower plasma sodium values (139.5 +/- 4.86 mmol/l) in the allopurinol-pretreated ARF group were found than in the ARF group without pretreatment, in the ARF group pretreated with enalapril, and in the sham SHR group (p = 0.029). The urinary sodium loss was greater in the enalapril-pretreated than in the allopurinol-pretreated ARF group (p = 0.047). Allopurinol and/or enalapril pretreatment decreased total vascular resistance (p = 0.003) in comparison with the sham SHR group.

CONCLUSION

Neither allopurinol nor enalapril nor both were protective against ischemia-reperfusion injury in SHR, nor altered glomerular filtration rate and UNOx in a favorable direction.

Iodinated contrast induced renal vasoconstriction is due in part to the downregulation of renal cortical and medullary nitric oxide synthesis

OBJECTIVES

The loss of renal function continues to be a frequent complication of the iodinated contrast agents used to perform diagnostic angiography and endovascular procedures. This study examined the hypothesis that contrast-induced renal injury is partly due to a decrease in cortical and medullary microvascular blood flow after the downregulation of endogenous renal cortical and medullary nitric oxide (NO) synthesis.

METHODS

Anesthetized male Sprague-Dawley rats (300 g) had microdialysis probes or laser Doppler fibers inserted into the renal cortex to a depth of 2 mm and into the renal medulla to a depth of 4 mm. Laser Doppler blood flow was continuously monitored, and the microdialysis probes were connected to a syringe pump and perfused in vivo at 3 muL/min with lactated Ringer's solution. Dialysate fluid was collected at time zero (basal) and 60 minutes after infusion of either saline or Conray 400 (6 mL/kg). Both groups were treated with saline carrier, N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME, 30 mg/kg), L-arginine (400 mg/kg), or superoxide dismutase (10,000 U/kg), an oxygen-derived free radical scavenger. Dialysate was analyzed for total NO and eicosanoid synthesis. The renal cortex and medulla were analyzed for inducible NO synthase (iNOS), cyclooxygenase-2 (COX2), prostacyclin synthase, and prostaglandin E(2) (PGE(2)) synthase content by Western blot analysis.

RESULTS

Conray caused a marked decrease in cortical and medullary blood flow with a concomitant decrease in endogenous cortical NO, PGE(2), and medullary NO synthesis. The addition of L-NAME to the Conray further decreased cortical and medullary blood flow and NO synthesis, which were restored toward control by L-arginine. Neither L-NAME nor L-arginine (added to the Conray) altered cortical or medullary eicosanoids release. Medullary PGE(2) synthesis decreased when superoxide dismutase was added to the Conray treatment, suggesting that oxygen-derived free radicals had a protective role in maintaining endogenous medullary PGE(2) synthesis after Conray treatment. Conray did not significantly alter iNOS, COX-2, prostacyclin synthase, or PGE(2) synthase content.

CONCLUSIONS

These findings suggest that the downregulation of renal cortical and medullary NO synthesis contributes to the contrast-induced loss of renal cortical and medullary microvascular blood flow. Preservation of normal levels of renal cortical and medullary NO synthesis may help prevent or lessen contrast-induced renal vasoconstriction and lessen contrast-induced renal injury found after diagnostic and therapeutic endovascular procedures.

N-acetylcysteine and contrast-induced nephropathy in primary angioplasty

BACKGROUND

Patients with acute myocardial infarction undergoing primary angioplasty are at high risk for contrast-medium-induced nephropathy because of hemodynamic instability, the need for a high volume of contrast medium, and the lack of effective prophylaxis. We investigated the antioxidant N-acetylcysteine for the prevention of contrast-medium-induced nephropathy in patients undergoing primary angioplasty.

METHODS

We randomly assigned 354 consecutive patients undergoing primary angioplasty to one of three groups: 116 patients were assigned to a standard dose of N-acetylcysteine (a 600-mg intravenous bolus before primary angioplasty and 600 mg orally twice daily for the 48 hours after angioplasty), 119 patients to a double dose of N-acetylcysteine (a 1200-mg intravenous bolus and 1200 mg orally twice daily for the 48 hours after intervention), and 119 patients to placebo.

RESULTS

The serum creatinine concentration increased 25 percent or more from baseline after primary angioplasty in 39 of the control patients (33 percent), 17 of the patients receiving standard-dose N-acetylcysteine (15 percent), and 10 patients receiving high-dose N-acetylcysteine (8 percent, P<0.001). Overall in-hospital mortality was higher in patients with contrast-medium-induced nephropathy than in those without such nephropathy (26 percent vs. 1 percent, P<0.001). Thirteen patients (11 percent) in the control group died, as did five (4 percent) in the standard-dose N-acetylcysteine group and three (3 percent) in the high-dose N-acetylcysteine group (P=0.02). The rate for the composite end point of death, acute renal failure requiring temporary renal-replacement therapy, or the need for mechanical ventilation was 21 (18 percent), 8 (7 percent), and 6 (5 percent) in the three groups, respectively (P=0.002).

CONCLUSIONS

Intravenous and oral N-acetylcysteine may prevent contrast-medium-induced nephropathy with a dose-dependent effect in patients treated with primary angioplasty and may improve hospital outcome. (ClinicalTrials.gov number, NCT00237614[ClinicalTrials.gov]).

Contrast-induced nephropathy: Pharmacological prophylaxis

Contrast media-associated acute renal failure represents the third most common cause of in-hospital renal function deterioration after decreased renal perfusion and post-operative renal insufficiency. Although generally benign, this complication is associated with a mortality rate ranging from 3.8 to 64%, depending on the increase of creatinine concentration. Multiple drugs have been tested in an attempt to prevent this complication. Central to the pathophysiology of contrast-induced nephrotoxicity (CIN) is an alteration in renal hemodynamics. In an effort to reverse these hemodynamic changes, vasodilators and diuretics have been tested as prophylactic drugs. However, their effectiveness has not been confirmed. Recently, considerable interest has resulted from the initial positive data on the effectiveness of prophylactic administration of antioxidant compounds, such as acetylcysteine and ascorbic acid. In this review, we focus on the effectiveness of pharmacologic therapies for preventing CIN.

N-acetylcysteine ameliorates amphotericin-induced nephropathy in rats

BACKGROUND

Amphotericin B may cause acute reduction in renal function. N-acetylcysteine (NAC) has a renoprotective activity in several nephrotoxic renal insults, but its effect on amphotericin-induced renal failure has not been investigated yet.

METHODS

Acute renal failure was induced in 30 Sprague-Dawley rats by a single intraperitoneal injection of amphotericin B (50 mg/kg). NAC (10 mg/kg) in isotonic saline or isotonic saline alone were administered daily for 4 days, starting 1 day before the amphotericin B injection. Glomerular filtration rate (GFR) was assessed using 99m-technetium diethylene triaminepentaacetic acid. Before and following amphotericin B administration, a 24-hour urine collection was performed for sodium, potassium and magnesium determination. The kidneys were preserved for pathologic examination.

RESULTS

Amphotericin B induced a significant decrease of GFR in both groups. Four days after amphotericin injection the GFR in the NAC-treated group was significantly higher than in the control group (0.62 +/- 0.20 vs. 0.46 +/- 0.14 ml/min, p = 0.042). Histologic signs of acute tubular necrosis were attenuated in the NAC-treated group. There were no significant differences between the groups in sodium, potassium and magnesium urine excretion after amphotericin injection.

CONCLUSIONS

NAC treatment exerted a renoprotective effect on deterioration of GFR in a rat model of amphotericin-induced renal failure. No functional protection on tubular function, as obviated by similar polyuria and urine losses of potassium and magnesium in both groups, was observed.

EFFECTS OF N-ACETYL-l-CYSTEINE ON RENAL HAEMODYNAMICS AND FUNCTION IN EARLY ISCHAEMIA-REPERFUSION INJURY IN RATS

1. Renal ischaemia-reperfusion (IR) severely compromises kidney function and has been shown to cause persistent abnormalities in intrarenal blood flow. The aim of the present study was to examine whether N-acetyl-L-cysteine (NAC), a thiol-containing anti-oxidant, improves renal haemodynamics and function during early reperfusion in rats subjected to renal IR. 2. Male Sprague-Dawley rats were divided into groups receiving either isotonic saline (IR-Saline; n = 8) or NAC (IR-NAC; n = 8) prior to (200 mg/kg, i.p., 24 and 12 h before acute experimentation) and during acute renal clearance experiments (bolus 150 mg/kg followed by a continuous infusion of 43 mg/kg per h, i.v.). During acute experimentation, thiobutabarbital-anaesthetized rats were subjected to a right-sided nephrectomy, followed by left kidney IR (40 min renal artery occlusion). Left kidney function and blood flow and intrarenal cortical and outer medullary perfusion measured by laser-Doppler flowmetry was analysed at baseline, during ischaemia and for 80 min of reperfusion. 3. Renal IR produced an approximate 85% reduction in glomerular filtration rate (GFR) and a pronounced increase in fractional urinary sodium excretion, throughout reperfusion, with no statistically significant differences between groups. 4. During reperfusion, total renal blood flow and cortical and outer medullary perfusion rapidly returned to levels not significantly different from baseline in both groups. The relative increase in renal vascular resistance in response to IR was more pronounced in NAC-treated rats compared with saline-treated animals (P < 0.05). 5. In conclusion, treatment with NAC did not improve kidney function during the first 80 min after renal IR. In addition, the marked reduction in GFR following reperfusion was not associated with any detectable abnormalities in intrarenal perfusion.

ApoSense: a novel technology for functional molecular imaging of cell death in models of acute renal tubular necrosis

Purpose

Acute renal tubular necrosis (ATN), a common cause of acute renal failure, is a dynamic, rapidly evolving clinical condition associated with apoptotic and necrotic tubular cell death. Its early identification is critical, but current detection methods relying upon clinical assessment, such as kidney biopsy and functional assays, are insufficient. We have developed a family of small molecule compounds, ApoSense, that is capable, upon systemic administration, of selectively targeting and accumulating within apoptotic/necrotic cells and is suitable for attachment of different markers for clinical imaging. The purpose of this study was to test the applicability of these molecules as a diagnostic imaging agent for the detection of renal tubular cell injury following renal ischemia.

Methods

Using both fluorescent and radiolabeled derivatives of one of the ApoSense compounds, didansyl cystine, we evaluated cell death in three experimental, clinically relevant animal models of ATN: renal ischemia/reperfusion, radiocontrast-induced distal tubular necrosis, and cecal ligature and perforation-induced sepsis.

Results

ApoSense showed high sensitivity and specificity in targeting injured renal tubular epithelial cells in vivo in all three models used. Uptake of ApoSense in the ischemic kidney was higher than in the non-ischemic one, and the specificity of ApoSense targeting was demonstrated by its localization to regions of apoptotic/necrotic cell death, detected morphologically and by TUNEL staining.

Conclusion

ApoSense technology should have significant clinical utility for real-time, noninvasive detection of renal parenchymal damage of various types and evaluation of its distribution and magnitude; it may facilitate the assessment of efficacy of therapeutic interventions in a broad spectrum of disease states.

N-acetylcysteine for prevention of radiographic contrast material-induced nephropathy: is the intravenous route best?

Use of oral N-acetylcysteine for preventing radiographic contrast material-induced nephropathy (RCIN) has become widespread, despite conflicting results from clinical trials and meta-analyses. The variability in study results may reflect differences in baseline risks in study patients, hydration regimens, choice of contrast agent, definition of RCIN, and the oral dosage formulation of N-acetylcysteine used. Injectable N-acetylcysteine recently has become available in the United States. Although oral N-acetylcysteine regimens are typically administered during a 48-hour period, more rapid intravenous administration could offer an important advantage for urgent procedures such as coronary angiography. However, the three published studies in which intravenous N-acetylcysteine protocols were used have produced divergent results, likely because of substantially different dosage regimens. With few intravenous studies available, clinicians may look to more broadly studied oral regimens to estimate equivalent intravenous dosages. In the oral studies, however, a wide range of formulations were used, and the bioavailability of each product was uncertain. In addition, the intravenous route circumvents first-pass metabolism, resulting in less glutathione production, perhaps compromising the antioxidant effects of N-acetylcysteine administration. Overall, little evidence exists that any studied N-acetylcysteine protocol improves clinical outcomes in terms of reducing length of hospital stay, need for dialysis, or mortality. Furthermore, N-acetylcysteine may directly affect serum creatinine level, which all clinical trials to date have used as a primary outcome measure. If oral or intravenous N-acetylcysteine is used with the intention of preventing RCIN, more established preventive measures should not be overlooked, including adequate hydration with isotonic saline, avoidance of potentially nephrotoxic drugs, and use of iso-osmolar radiographic contrast media.

Epidermal growth factor activates nuclear factor-κB in human proximal tubule cells

The promotion of cell survival and regeneration in acute renal failure (ARF) is important for the restitution of renal function. Epidermal growth factor (EGF) has been implicated in the regulation of cell proliferation. We provide evidence for a direct link between EGF, nuclear factor-κB (NF-κB), and cell cycle regulation (cyclin D1). EGF was found to stimulate NF-κB-dependent gene transcription and DNA binding. In addition, EGF stimulated cyclin D1 promoter activity as well as cyclin D1 expression. Moreover, inhibition of NF-κB caused a pronounced reduction of EGF-induced cyclin D1 promoter activity. Furthermore, both EGF-mediated NF-κB activation and cyclin D1 expression were inhibited by coexpression of super IκB. Taken together, these data identify NF-κB and cyclin D1 as downstream targets of EGF and establish a molecular link between stimulation of EGF via activation of NF-κB and cyclin D1 expression in human proximal tubular cells.

Magnesium Supplementation Combined with N-Acetylcysteine Protects against Postischemic Acute Renal Failure

Magnesium is a potent vasodilator whose effects have not been evaluated in renal ischemia. The antioxidant properties of N-acetylcysteine (NAC) partially protect animals from ischemic/reperfusion injury. This study was designed to evaluate magnesium supplementation, alone or combined with NAC, on ischemic acute renal failure. Rats were maintained on normal diets, supplemented or not with MgCl(2).6H(2)O (1% in drinking water) for 23 d, and some rats received NAC (440 mg/kg body wt) on days 20 to 23. On day 21, ischemia was induced by clamping both renal arteries for 30 min. Five groups were studied: Normal, ischemia, ischemia+magnesium, ischemia+NAC, and ischemia+magnesium+NAC. GFR (inulin clearance), renal blood flow (RBF), FEH(2)O, and FENa were determined. Serum magnesium was decreased in ischemia-only rats. Magnesium prevented postischemia GFR and RBF decreases but did not protect against tubular damage. However, NAC completely restored the tubular damage induced by ischemia/reperfusion. Semiquantitative immunoblotting showed that NAC prevented the decreased expression of Na-K-2Cl co-transporter and aquaporin 2 after renal ischemia/reperfusion. Untreated rats with acute renal failure demonstrated markedly decreased endothelial nitric oxide synthase expression. Significantly, treatment with NAC, magnesium, or both completely inhibited downregulation of endothelial nitric oxide synthase. The tubular necrosis scores were lower in rats that were treated with NAC alone or with the magnesium-NAC combination. Magnesium prevented postischemia GFR and RBF decreases but did not protect against tubular damage. The NAC protected tubules from ischemia, decreased infiltrating macrophages/lymphocytes, and had a mild protective effect on GFR. In ischemic/reperfusion injury, renal function benefits more from the magnesium-NAC combination than from magnesium alone.