Biology of acute renal failure: therapeutic implications

Synovial interlukin-6 affects apoptosis induction via nuclear factor kappa-B and fractalkine pathway during adjuvant arthritis

Background: Apoptosis disruptions play substantial roles in pathogenesis of arthritis and its symptoms. Cytokines and their intracellular signaling have pivotal roles in arthritis pathophysiology. This study aimed to investigate the relationship between synovial Interleukin-6 (IL-6), nuclear factor kappa-B (NF-ĸB), and fractalkine (FKN) in the changes of edema and apoptosis during adjuvantinduced knee arthritis. Methods: A total of 240 male Wistar rats were divided into different groups. Arthritis was evoked and the knee edema changes were evaluated by Vernier caliper. Synovial IL-6 was assayed by rat standard ELISA kit. Levels of NF-ĸB, fractalkine, and apoptotic indicators in the synovium were evaluated by Western blot method. Results were expressed as Mean± SEM. To analyze within-group variations, repeated measures ANOVA, followed by post hoc Tukey's test was used (SPSS, 16). Independent samples t test was used to designate significant differences in knee diameter, synovial level of IL-6, apoptotic markers, NF-ĸB, and FKN between groups. Significance level was set at P≤ 0.05. Results: The injection of Complete Freund's Adjuvant (CFA) caused intense knee edema (P< 0.001), which was reduced by implementing anti-IL-6 (P< 0.001), anti-FKN (P< 0.001), Inh-NF-ĸB (P< 0.001), and anti-FKN+ Inh NF-kB (P< 0.001). The results indicated elevated levels of apoptotic markers during the acute phase (P = 0.010), along with an increase in IL-6 (P< 0.001), NF-ĸB (P< 0.001), and FKN (P= 0.030). Although IL-6 (P< 0.001), NF-ĸB (P= 0.001), and FKN (P= 0.007) levels elevation continued during the chronic phase, the apoptosis markers decreased in this phase (P= 0.050). The findings revealed that Anti-IL-6 treatment during different phases of the study could change the synovial NF-ĸB and FKN. Conclusion: It seems that time-dependent variations in apoptotic markers level may be involved in pathogenesis of adjuvant-induced knee arthritis. In conclusion, synovial IL-6 through NF-ĸB- FKN pathway can play an important role in this process.

Neutrophil peptidyl arginine deiminase-4 has a pivotal role in ischemia/reperfusion-induced acute kidney injury

Ischemia/reperfusion is a common cause of acute kidney injury (AKI). However, mechanisms underlying the sudden loss in kidney function and tissue injury remain to be fully elucidated. Here, we investigated the role of peptidyl arginine deiminase-4 (PAD4), which converts arginine to citrulline and plays a role in epigenetic regulation and inflammation, in renal ischemia/reperfusion injury. PAD4 expression was highly induced in infiltrating leukocytes 24 hours following renal ischemia and reperfusion. This induction was accompanied by citrullination of histone H3 and formation of neutrophil extracellular traps in kidneys of wild-type mice. By contrast, PAD4-deficient mice did not form neutrophil extracellular traps, expressed lower levels of pro-inflammatory cytokines and were partially protected from renal ischemia/reperfusion-induced AKI. Furthermore, PAD4-deficient mice recovered kidney function 48 hours after ischemia/reperfusion, whereas kidney function in the wild-type mice progressively worsened. Administration of DNase I, which degrades neutrophil extracellular traps or the PAD-specific inhibitor YW3-56 before ischemia, partially prevented renal ischemia/reperfusion-induced AKI. Notably, transfer of neutrophils from wild-type, but not from PAD4-deficient mice, was sufficient to restore renal neutrophil extracellular trap formation and impair kidney function following renal ischemia/reperfusion. Thus, neutrophil PAD4 plays a pivotal role in renal ischemia/reperfusion-induced AKI.

The Impact of Synovial NF-κB Activation on Apoptosis Pattern Change During Adjuvant-induced Inflammation

Introduction:

Apoptosis dysregulation plays a substantial role in the pathophysiology of chronic inflammation and its related symptoms such as edema. Regulation of NF-κB activation is involved in apoptosis pattern change. The current study aimed at verifying the effects of local inflammation on edema and changes in apoptotic markers, and investigating the possible role of NF-κB in apoptosis pattern change during different stages of complete Freund’s adjuvant (CFA)-induced knee arthritis in rats.

Methods:

A total of 96 male Wistar rats were divided into different experimental groups. Arthritis was evoked into the right knee articular joint. Changes made in knee edema were assessed by caliper on the days 0, 7, 14, and 21 of the study. Synovial NF-κB and levels of apoptotic markers were evaluated during different stages of the study using Western blot technique.

Results:

CFA injection caused intense edema during the whole study period. Synovial NF-κB level increased during the whole study period. The level of apoptotic markers increased during the acute phase of study. But during chronic phase, the apoptosis level decreased. Inh-NF-κB administration increased synovial apoptosis during the whole study period.

Conclusion:

It seems that apoptosis pattern change plays an important role in the progression and modulation of CFA-induced inflammation and its related symptoms. Also, it can be concluded that synovial NF-κB had a crucial role in synovial apoptosis change during the study period.

Effects of fenofibrate, a PPAR-α ligand, on the haemodynamics of glycerol-induced renal failure in rats

The modulating effect of peroxisome proliferator-activated receptor α ligand on haemodynamic effects of phenylepherine (PE), angiotensin II (AII), endothelin 1 (ET1), acetylcholine (Ach), sodium nitroprusside (SNP) and isoproterenol (ISO) were evaluated in glycerol-induced acute kidney injury in rats. The effect of PE on fenofibrate-treated animals was a dose-dependent increase in mean arterial blood pressure (MAP). For AII and ET1, MAP was also increased for the fenofibrate group but not in a dose-dependent fashion. On the medullary blood flow (MBF), while the lower doses of PE and AII increased the perfusion unit on the fenofibrate-treated group, the higher doses decreased the perfusion unit. The ET1 increased the perfusion unit on this group but not in dose-dependent fashion. The effects of PE and AII on the cortical blood flow (CBF) of fenofibrate-treated group is similar to that of MBF for the same group but not for ET1. The effect of Ach, SNP and ISO in all the groups was the decrease in MAP. ISO caused dose-dependent increase in MBF of fenofibrate-treated group. The effect of Ach, SNP and ISO on the CBF perfusion unit was that of the increase for the fenofibrate-treated group. The study showed that fenofibrate did not attenuate increased blood pressure induced by PE, AII and ET1 but caused enhanced vasodilation by Ach, SNP and ISO.

Endotoxemia alters tight junction gene and protein expression in the kidney

Intact tight junctional (TJ) proteins are required for tubular ion transport and waste excretion. Disruption of TJs may contribute to a decreased glomerular filtration rate in acute kidney injury (AKI) via tubular backleak. The effect of LPS-mediated AKI on murine TJs has not been studied extensively. We hypothesized LPS endotoxin administration to mice would disrupt tubular TJ proteins including zonula occludens-1 (ZO-1), occludin, and claudins. ZO-1 and occludin immunofluorescence 24 h post-LPS revealed a marked change in localization from the usual circumferential fencework pattern to one with substantial fragmentation. Renal ZO-1 expression was significantly reduced 24 h after LPS (decrease of 56.1 ± 7.4%, P < 0.001), with subsequent recovery. ZO-1 mRNA expression was increased 24 h post-LPS (4.34 ± 0.87-fold, P = 0.0019), suggesting disruption of ZO-1 protein is not mediated by transcriptional regulation, but rather by degradation or changes in translation. Similarly, claudin-4 protein expression was decreased despite elevated mRNA. LPS administration resulted in dephosphorylation of occludin and fragmented tubular redistribution. Protein expression of claudin-1, and -3 was increased after LPS. ZO-1, occludin, and claudin-1, -3, and -4 gene expression were increased 48 h after LPS, suggesting a renal response to strengthen TJs following injury. Interestingly, reduced mRNA expression was found only for claudin-8. This study provides further support that LPS-induced AKI is associated with structural injury and is not merely due to hemodynamic changes.

Acute renal venous obstruction is more detrimental to the kidney than arterial occlusion: implication for murine models of acute kidney injury

In this study, we compared the traditional murine model with renal pedicle clamp with models that clamped the renal artery or vein alone as well as to a whole body ischemia-reperfusion injury (WBIRI) model. Male C57BL/6J mice underwent either clamping of the renal artery, vein, or both (whole pedicle) for 30 or 45 min followed by reperfusion, or 10 min of cardiac arrest followed by resuscitation up to 24 h. After 30 min of ischemia, the mice with renal vein clamping showed the mostly increased serum creatinine and the most severe renal tubule injury. After 45 min of ischemia, all mice with renal vasculature clamping had a comparable increase in serum creatinine but the renal tubule injury was most severe in renal artery-clamped mice. Renal arterial blood flow was most decreased in mice with a renal vein clamp compared with a renal artery or pedicle clamp. A 30-or 45-min renal ischemia time led to a significant increase in the protein level of interleukin-6, keratinocyte-derived chemokine (KC), and granular colony-stimulating factor in the ischemic kidney, but the KC was the highest in the renal pedicle-clamped kidney and the lowest in the renal vein-clamped kidney. Of note, 10 min of WBIRI led to kidney dysfunction and structural injury, although less than longer time clamping of isolated renal vasculature. Our data demonstrate important differences in ischemic AKI models. Understanding these differences is important in designing future experimental studies in mice as well as clinical trials in humans.

Midkine antisense oligodeoxyribonucleotide inhibits renal damage induced by ischemic reperfusion

BACKGROUND

Midkine, a heparin-binding growth factor, is involved in the migration of inflammatory cells. The inflammatory cell migration to the tubulointerstitium of the kidney after ischemia/reperfusion (I/R) injury is attenuated in midkine gene-deficient mice, resulting in better preservation of the tubulointerstitium compared with wild-type mice. In the present investigation, we planned to evaluate the usefulness of antisense midkine for the therapy of ischemic renal failure.

METHODS

Midkine antisense phosphorothioate oligodeoxyribonucleotide (ODN) at a dose of 1 mg/kg in saline was intravenously administered to mice 1 day before or after I/R. The kidneys were removed for examination 1, 2, 3, and 7 days after I/R.

RESULTS

It was rapidly incorporated into proximal tubular epithelial cells, and inhibited midkine synthesis, leading to reduced migration of inflammatory cells to the injured epithelial layer. Consequently, the midkine antisense ODN-treated animals exhibited less severe renal damage than untreated or midkine sense ODN-treated animals 2 days after I/R as assessed by morphologic criteria and blood urea nitrogen (BUN) and serum creatinine levels. Midkine expression, BUN, and serum creatinine levels were not significantly different between injection of midkine antisense ODN before and after ischemic injury.

CONCLUSION

These results indicate that intravenous injection of midkine antisense ODN is a candidate for a novel therapeutic strategy against acute tubulointerstitial injury induced by I/R injury.

[Acute renal failure in critically-ill children. A preliminary study]

OBJECTIVE

To analyze the characteristics of acute renal failure (ARF) in critically-ill children and develop a protocol for a multicenter study.

METHODS

A prospective, descriptive study was performed in four pediatric intensive care units (PICU) over 5 months. Epidemiological, clinical and laboratory data from children aged between 7 days and 16 years with ARF were analyzed. Premature neonates were excluded.

RESULTS

There were 16 episodes of ARF in 14 patients and 62.5 % were male (mean 6 SD age: 50 +/- 49 months). The incidence of ARF was 2.5 % of PICU patients. The most frequent primary diseases were nephro-urological (50 %) and heart disease (31 %). The main risk factors for ARF were hypovolemia (44 %) and hypotension (37 %). Six patients (37.5 %) developed ARF following surgery (cardiac surgery in four, kidney transplantation in one and urological surgery in one). Furosemide was used in 13 patients (as continuous perfusion in nine), inotropes in nine and renal replacement therapy in 12. Medical complications were found in 94 % and some organic dysfunction was found in 81 %. The length of stay in the PICU was 21 +/- 21 days. The probability of death according to the Pediatric Risk of Mortality was 14 +/- 8 %. Five patients died (36 % of the patients and 31.2 % of ARF episodes).

CONCLUSIONS

The incidence of ARF in critically-ill children is low but remains a cause of high mortality and prolonged stay in the PICU. Mortality was caused not by renal failure but by multiple organ failure.

Endothelial injury and dysfunction: role in the extension phase of acute renal failure

The pathophysiology of ischemic acute renal failure (ARF) involves a complex interplay between renal hemodynamics, tubular and endothelial cell injury, and inflammatory processes. A growing body of evidence supports the contribution of altered renal vascular function, especially at the microvascular level, in initiating and subsequently extending the initial tubular injury. The extension phase of ischemic ARF involves continued reduction in renal perfusion, ongoing hypoxia, and inflammatory processes that occur during reperfusion and contribute to continued tubular cell injury. Vascular endothelial cell injury and dysfunction play a vital part in this extension phase. With injury, the endothelial cell loses its ability to regulate vascular tone, perfusion, permeability and inflammation/adhesion. This loss of regulatory function has a detrimental impact upon renal function. Vascular congestion, edema formation, diminished blood flow, and infiltration of inflammatory cells have been documented in the corticomedullary junction of the kidney. However, linking their genesis to microvascular endothelial injury and dysfunction has been difficult. New diagnostic and therapeutic approaches to ischemic ARF must incorporate these finding to devise early recognition strategies and therapeutic approaches.

Effect of antisense oligodeoxynucleotides for ICAM-1 on renal ischaemia-reperfusion injury in the anaesthetised rat

An antisense oligodeoxynucleotide (As-ODN) to the 3' untranslated region of the mRNA sequence expressing the intracellular adhesion molecule-1 (ICAM-1) was employed to determine ICAM-1's role in renal ischaemia-reperfusion injury in the rat. Wistar-Kyoto rats receiving i.v. either lipofectin-As-ODN (As-ODN group), lipofectin-reverse ODN (Rv-ODN group) or lipofectin (ischaemia control group) 8 h prior to study were anaesthetized and subjected to 30 min of renal artery occlusion. Renal haemodynamic and excretory parameters were monitored before and after renal ischaemia. On termination of the study renal tissue was subjected to histological and Western blot analysis. Renal blood flow decreased in the 3 h post-ischaemia period in the ischaemia control and Rv-ODN groups, but was maintained in the As-ODN group. Glomerular filtration rate was depressed initially but gradually increased to 10% above basal levels in the ischaemia control and Rv-ODN groups, but was below basal levels (20%) in the As-ODN group. There was a three- to fourfold increase in sodium and water excretion following ischaemia in the ischaemia control and reverse-ODN groups but not in the As-ODN treated group. The As-ODN ameliorated the histological evidence of ischaemic damage and reduced ICAM-1 protein levels to a greater extent in the medulla than cortex. These observations suggested that in the post-ischaemic period afferent and efferent arteriolar tone was increased with a loss of reabsorptive capacity which was in part due to ICAM-1. The possibility arises that the action of ICAM-1 at vascular and tubular sites in the deeper regions of the kidney contributes to the ischaemia-reperfusion injury.

Pathophysiology of ischaemic acute renal failure

This chapter summarizes the pathophysiology of ischaemic acute renal failure from both the experimental and clinical points of view. Traditionally, the abrupt fall in glomerular filtration rate (GFR) is thought to be due to an interplay of haemodynamic and tubular abnormalities. The intrarenal haemodynamic alterations include renal vasoconstriction, leukocyte-endothelium interactions and loss of blood flow and GFR autoregulation. During recent years it has become evident that pronounced outer medulary ischaemia makes an important contribution. In severe and prolonged ischaemia, the tubular epithelial cells can undergo either sublethal or lethal cell damage. Cell death occurs by necrosis and apoptosis. The different mechanisms of post-ischaemic cell damage are discussed. The post-ischaemic kidney also shows a dramatic capacity for recovery. During this recovery phase some of the damaged cells undergo de-differentiation--which is an important step in regeneration of the tubular epithelium. Recent evidence points to the possibility that infiltration of the kidney with bone-marrow-derived stem cells contributes to the repair process. The molecular mechanisms and the effect of growth factors are summarized.

Relative roles of endothelin-1 and angiotensin II in experimental post-ischaemic acute renal failure

BACKGROUND

The relative roles of endothelin (ET)-1 and angiotensin (ANG) II in post-ischaemic acute renal failure (ARF) have not been fully established so far. With the aim of contributing to this goal, we assessed in this study the effect of ANG II and ET-1 blockade on the course of post-ischaemic-ARF.

METHODS

Anaesthetized Wistar rats received i.v. either bosentan (a dual ET receptor antagonist; 10 mg/kg body weight) or losartan [ANG II type 1 (AT(1)) receptor antagonist; 5 or 10 mg/kg body weight] or both, 20 min before, during and 20 min after ischaemia. Rats in the control group received the vehicle via the same route. Survival and renal function were monitored up to 8 days after the ischaemic challenge, while haemodynamic parameters were measured 24 h after ARF.

RESULTS

Our results demonstrate that bosentan treatment has a more beneficial effect on experimental ARF than losartan. The survival rate was remarkably higher in bosentan-treated rats than in both rat groups treated with losartan. In the ARF group treated with bosentan, renal blood flow (RBF) was increased by 129% in comparison with the untreated ARF group, whereas in the losartan-treated ARF groups, RBF was only approximately 35 or 38% higher than in control ARF rats. The glomerular filtration rate was markedly higher in bosentan-treated rats than in all other ARF groups on the first and second day after ischaemia. Tubular cell injury was less severe in bosentan-treated rats than in the control ARF rats, but in losartan-treated groups it was similar to that in the ARF group. Concurrent blockade of both ET and AT(1) receptors did not improve ARF because this treatment induced a marked decrease in blood pressure.

CONCLUSIONS

These results suggest that ET-1 blockade is more efficient in improving the early course of post-ischaemic renal injury than ANG II inhibition, and that blockade of ET-1 might be effective in prophylaxis of ischaemic ARF.

Renal ischemia-reperfusion injury in the rat is prevented by a novel immune modulation therapy

BACKGROUND

Vasogen Inc.'s (Mississauga, Ontario, Canada) immune modulation therapy (IMT) is a therapy in which cells from the patient's own blood are modified by ex vivo exposure to specific physicochemical stressors, including oxidation, ultraviolet (UV) light, and an elevated temperature. The therapy has been shown to have a beneficial effect in models of inflammation and vascular diseases. This study tested the hypothesis that IMT can prevent renal ischemia-reperfusion (I/R) injury in rats.

METHODS

Whole blood was collected from syngeneic age-matched donors by cardiac puncture. It was treated with a combination of controlled physiochemical stressors consisting of elevated temperature, a gas mixture of medical oxygen containing ozone, and UV light. The treated blood (150 microL) was injected in the gluteal muscle. Control animals received the same volume of untreated blood or physiological saline. Transient (45 or 60 minutes) left-renal ischemia was produced with simultaneous contralateral nephrectomy in treated and control spontaneously hypertensive rats (SHR). Young and old male and female rats were studied. Plasma creatinine, diuresis, and the survival rates of each group were compared. Renal apoptosis-necrosis was estimated by DNA laddering, histology, and in situ terminal deoxynucleotidyl transferase assay. mRNA levels of several regulators of apoptosis-regeneration were determined in control and postischemic kidneys by Northern blotting.

RESULTS

IMT pretreatment of SHR significantly reduced renal I/R injury compared with equivalent placebo treatments consisting of untreated blood- or saline-injected SHR, as evidenced by a significant increase of the survival rate curves in young and old male SHR, which correlated with 24-hour postischemic diuresis. The increases in plasma creatinine following renal I/R were significantly lower in IMT-treated young male and old female SHR compared with saline or untreated blood-injected controls. Dilution analysis showed that the protective effect of treated blood was lost by dilution. Loss of epithelial cells was reduced in IMT-treated rats, with a significant decline in the peak of apoptosis 12 hours after acute ischemic renal injury. IMT did not modify the pattern of mRNA levels of several genes involved in the inflammation and regeneration processes.

CONCLUSION

Our data demonstrate that IMT prevents the destruction of kidney tissue and the resulting animal death caused by renal I/R injury.

Microvascular endothelial injury and dysfunction during ischemic acute renal failure

The pathophysiology of ischemic acute renal failure (ARF) appears to involve a complex interplay between renal hemodynamics, tubular injury, and inflammatory processes. While the current paradigm of the pathophysiology of ischemic ARF invokes both sublethal and lethal tubular injury as being of paramount importance to diminished renal function, a growing body of evidence supports the contribution of altered renal vascular function in potentially initiating and subsequently extending the initial tubular injury. We propose that the "extension phase" of ischemic ARF involves alterations in renal perfusion, continued hypoxia, and inflammatory processes that all contribute to continued tubular cell injury. Vascular endothelial cell injury and dysfunction play a vital part in this extension phase. In the constitutive state the endothelium regulates migration of inflammatory cells into tissue, vascular tone and perfusion, vasopermeability, and prevents coagulation. Upon injury, the endothelial cell loses its ability to regulate these functions. This loss of regulatory function can have a subsequent detrimental impact upon renal function. Vascular congestion, edema formation, diminished blood flow, and infiltration of inflammatory cells have been documented in the corticomedullary junction of the kidney, but linking their genesis to vascular endothelial injury and dysfunction has been difficult. However, new investigative approaches, including multiphoton microscopy and the Tie2-GFP mouse, have been developed that will further our understanding of the roles endothelial injury and dysfunction play in the pathophysiology of ischemic ARF. This knowledge should provide new diagnostic and therapeutic approaches to ischemic ARF.

Endothelial injury and dysfunction in ischemic acute renal failure

Ischemic acute renal failure is the most common cause of acute renal failure in hospitalized patients and has an average mortality rate of 50%. Although epithelial and vascular smooth muscle cell abnormalities have been clearly delineated in association with this condition, the extent of endothelial injury and dysfunction has been difficult to document, primarily for anatomic reasons. However, endothelial tight junction separation and endothelial cell detachment, blebbing, and necrosis have been observed after ischemia in other organs. In addition, adenosine triphosphate depletion studies in cultured endothelial cells have demonstrated that multiple actin-based alterations occur in a reversible and duration-dependent fashion. After an ischemic insult, total renal blood flow returns toward normal, but marked, regional alterations occur. Most affected is the outer medullary or corticomedullary junction region where blood flow remains approximately 10% of normal. In this area, the microvasculature becomes congested. Interstitial edema, red blood cell trapping, leukocyte adherence, and extravasation all contribute to this congestion. Increased expression of both P selectin and E selectin has been documented in renal endothelial cells after ischemic injury, and treatment with antibodies to either intercellular adhesion molecule-1, P selectins, or E selectins has been shown to minimize renal injury. During ischemia in vivo and adenosine triphosphate depletion in cell culture studies, F-actin destruction occurs, with polymerization leading to accumulation of intracellular actin aggregates. By using multiphoton microscopy, Voxx software, and the Tie-2 mouse with selective endothelial cell green fluorescent protein expression driven by the Tie-2 promoter, we have been able to identify macrovascular and microvascular endothelial cells in four dimensions (three dimensions plus time) intravitally. By using Texas red-labeled large molecular weight dextrans, we can document blood flow and vascular dysfunction. Intravital studies using multiphoton imaging techniques can now be conducted to identify and quantify endothelial cell injury and dysfunction in functioning organs.

Acute renal failure

Acute renal failure is characterized by an increase in the blood concentration of creatinine and nitrogenous waste products and by the inability of the kidney to appropriately regulate fluid and electrolyte homeostasis. There are many different causes of acute renal failure in children, including prerenal disease, intrinsic renal failure, which includes ischemic hypoxic insults, and obstructive uropathy. This review will focus on hypoxic/ischemic acute renal failure, the most common causes of hospital acquired acute renal failure in children. This review will briefly discuss the epidemiology and incidence of acute renal failure in pediatric patients and review new insights into the pathogenesis of acute renal failure. including hemodynamic alterations induced by alterations in nitric oxide and endothelin metabolism, the role of the inflammatory response, and alteration in polarity in the acute renal failure. The therapy of acute renal failure has changed substantially during the past few years. Controlled trials (in adults) to test the efficacy of "renal dose" dopamine have shown that it is ineffective, and hemofiltration has become increasingly popular as a choice of therapy for acute renal failure.

Acute renal failure in the critically ill patient

This article focuses on the epidemiology, pathogenesis, and prevention of the most common forms of acute renal failure encountered in the critically ill. These include pre-renal azotemia and acute tubular necrosis that occurs postoperatively, in patients with rhabdomyolysis, or as a complication of sepsis. In addition, some unusual causes of acute renal failure that occur predominantly in the intensive care unit are briefly discussed.

Midkine is involved in neutrophil infiltration into the tubulointerstitium in ischemic renal injury

Midkine (MK) is a multifunctional heparin-binding protein and promotes migration of neutrophils, macrophages, and neurons. In the normal mouse kidney, MK is expressed in the proximal tubules. After renal ischemic reperfusion injury, its expression in proximal tubules was increased. Immediate increase of MK expression was found when renal proximal tubular epithelial cells in culture were exposed to 5 mM H(2)O(2). Histologically defined tubulointerstitial damage was less severe in MK-deficient (Mdk(-/-)) than in wild-type (Mdk(+/+)) mice at 2 and 7 days after ischemic reperfusion injury. Within 2 days after ischemic injury, inflammatory leukocytes, of which neutrophils were the major population, were recruited to the tubulointerstitium. The numbers of infiltrating neutrophils and also macrophages were lower in Mdk(-/-) than in Mdk(+/+) mice. Induction of macrophage inflammatory protein-2 and macrophage chemotactic protein-1, chemokines for neutrophils and macrophages, respectively, were also suppressed in Mdk(-/-) mice. Furthermore, renal tubular epithelial cells in culture expressed macrophage inflammatory protein-2 in response to exogenous MK administration. These results suggested that MK enhances migration of inflammatory cells upon ischemic injury of the kidney directly and also through induction of chemokines, and contributes to the augmentation of ischemic tissue damage.

N-acetyl-L-cysteine improves renal medullary hypoperfusion in acute renal failure

This study evaluated the effects of N-acetyl-L-cysteine (NAC), a free radical scavenger, and N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthesis inhibitor, on the changes in renal function, intrarenal blood flow distribution (laser-Doppler flowmetry), and plasma peroxynitrite levels during the acute renal failure (ARF) produced by inferior vena cava occlusion (IVCO; 45 min) in anesthetized rats. Renal blood flow fell on reperfusion (whole kidney by -45.7%; cortex -58.7%, outer medulla -62.8%, and papilla -47.7%); glomerular filtration rate (GRF) also decreased (-68.6%), whereas fractional sodium excretion (FE(Na%)) and peroxynitrite and NO/NO plasma levels increased (189.5, 46.5, and 390%, respectively) after ischemia. Pretreatment with L-NAME (10 microg. kg(-1). min(-1)) aggravated the fall in renal blood flow seen during reperfusion (-60%). Pretreatment with NAC (150 mg/kg bolus + 715 microg. kg(-1). min(-1) iv) partially prevented those changes in renal function (GFR only fell by -29.2%, and FE(Na%) increased 119.4%) and laser-Doppler blood flow, especially in the outer medulla, where blood flow recovered to near control levels during reperfusion. These beneficial effects seen in rats given NAC seem to be dependent on the presence of NO, because they were abolished in rats pretreated with L-NAME. Also, the antioxidant effects of NAC prevented the increase in plasma peroxynitrite after ischemia. In conclusion, NAC ameliorates the renal failure and the outer medullary vasoconstriction induced by ICVO, effects that seem to be dependent on the presence of NO and the scavenging of peroxynitrite.

Reactive oxygen species and acute renal failure

Acute renal failure is commonly due to acute tubular necrosis (ATN), the latter representing an acute, usually reversible loss of renal function incurred from ischemic or nephrotoxic insults occurring singly or in combination. Such insults instigate a number of processes-hemodynamic alterations, aberrant vascular responses, sublethal and lethal cell damage, inflammatory responses, and nephron obstruction-that initiate and maintain ATN. Eventually, reparative and regenerative processes facilitate the resolution of renal injury and the recovery of renal function. Focusing mainly on ischemic ATN, this article reviews evidence indicating that the inordinate or aberrant generation of reactive oxygen species (ROS) may contribute to the initiation and maintenance of ATN. This review also discusses the possibility that ROS may instigate adaptive as well as maladaptive responses in the kidney with ATN, and raises the possibility that ROS may participate in the recovery phase of ATN.

Changes of urinary alpha1-microglobulin in the assessment of prognosis in renal transplant recipients

BACKGROUND

After transplantation, even if the graft starts functioning immediately, there are morphological and functional changes in tubular structures. In addition, acute allograft rejection causes damage in the tubular epithelium, tubular basement membrane, and intertubular connective tissue. It also affects the functional capacity of proximal tubular cells resulting in impaired reabsorption and thus increased urinary excretion of low molecular weight proteins.

METHODS

We present a double-antibody radioimmunoassay for determination of the concentration of alpha1-microglobulin (alpha1 M) in urine. It was used to measure urinary excretion of alpha1 M approximately once a week during the first 1-6 posttransplant weeks in 136 consecutive patients: 30 patients developing acute rejection (75 24-hr urine samples) and 106 patients with stable graft function (223 24-hr urine samples). The results are expressed as alpha1 M/creatinine ratios.

RESULTS

Approximately 8 days after transplantation the mean (+/-SD) urinary alpha1 M/creatinine ratio of all patients was 17.0+/-14.8 mg/mmol, being about the same both in patients with uncomplicated posttransplantation course (16.3+/-14.0 mg/mmol) and in those who later developed rejection (19.3+/-15.1 mg/mmol), but about 60-fold higher than in healthy controls (0.27+/-0.15 mg/mmol). At that time, when all patients were included there was a correlation (r=0.3465, P<0.001) between alpha1 M/creatinine ratio and duration of cold ischemia. Thereafter, during the second week alpha1 M/creatinine ratio decreased in 89% of patients with stable graft function, but only in 14% of patients who later developed rejection (P<0.001). On the contrary, a significant increase (P<0.01) of alpha1 M/creatinine ratio was observed 4 to 1 day before rejection in all 15 patients, who had urines collected at that time. At the end of the follow-up period, alpha1 M/creatinine ratio in patients with rejection was 3-fold compared with the nonrejecting patients, and 100-fold compared with the healthy controls.

CONCLUSION

These results show that cadaveric transplantation results in impaired low molecular weight protein reabsorption, the degree of dysfunction relating to the duration of cold ischemia, and suggest that during the posttransplant weeks decreasing alpha1 M/creatinine ratio in consecutively collected urine samples indicates improved tubular function and in most cases rules out development of acute rejection.

Cell biology and molecular mechanisms of injury in ischemic acute renal failure

The pathogenesis of acute renal failure has been attributed to persistent vasoconstriction and leukocyte-endothelial interactions, resulting in inflammation and compromise of local blood flow to the outer medulla, the loss of tubular epithelial cell polarity with multiple functional sequelae, necrosis or apoptosis of epithelial cells, and the de-differentiation, migration and proliferation of surviving cells. In this paper, the authors present their views of pathophysiology of ischemic acute renal failure.

Mouse proximal tubular cell-cell adhesion inhibits apoptosis by a cadherin-dependent mechanism

Adhesion of epithelial cells to matrix is known to inhibit apoptosis. However, the role of cell-cell adhesion in mediating cell survival remains uncertain. Primary cultures of mouse proximal tubular (MPT) cells were used to examine the role of cell-cell adhesion in promoting survival. When MPT cells were deprived of both cell-matrix and cell-cell adhesion, they died by apoptosis. However, when incubated in agarose-coated culture dishes (to prevent cell-matrix adhesion) and at high cell density (to allow cell-cell interactions), MPT cells adhered to one another and remained viable. Expression of E-cadherin among suspended, aggregating cells increased with time. A His-Ala-Val (HAV)-containing peptide that inhibits homophilic E-cadherin binding prevented cell-cell aggregation and promoted apoptosis of MPT cells in suspension. By contrast, inhibition of potential beta(1)-integrin-mediated interactions between cells in suspension did not prevent either aggregation or survival of suspended cells. Aggregation of cells in suspension activated phosphatidylinositol 3-kinase (PI3K), an event that was markedly reduced by the presence of the HAV peptide. LY-294002, an inhibitor of PI3K, also inhibited survival of suspended cells. In summary, we provide novel evidence that MPT cells, when deprived of normal cell-matrix interactions, can adhere to one another in a cadherin-dependent fashion and remain viable. Survival of aggregated cells depends on activation of PI3K.

New perspectives for prevention/treatment of acute renal failure

Acute renal failure continues to be a difficult clinical problem in critically ill patients, despite advances in critical care and dialysis. This review focuses on some of the current issues in the nondialytic and dialytic management of these patients. Critical analysis of some still frequently used drugs in these patients such as diuretics and dopamine in so-called 'renal doses' has revealed little beneficial effect. Recent data are in conflict with previous suggestions that biocompatible membranes have a positive effect on the recovery of renal function and on patient mortality. The choice between intermittent haemodialysis and continuous renal replacement therapy should be made on an individual basis and not on the basis of 'dogmatic' opinion.

Acute renal failure. II. Experimental models of acute renal failure: imperfect but indispensable

Acute renal failure (ARF) due to ischemic or toxic renal injury, a clinical syndrome traditionally referred to as acute tubular necrosis (ATN), is a common disease with a high overall mortality of approximately 50%. Little progress has been made since the advent of dialysis more than 30 years ago in improving this outcome. During this same period, a considerable amount of basic research has been devoted to elucidating the pathophysiology of ATN. The ultimate goal of this research is to facilitate the development of therapeutic interventions that either prevent ARF, ameliorate the severity of tubular injury following an acute ischemic or toxic renal insult, or accelerate the recovery of established ATN. This research endeavor has been highly successful in elucidating many vascular and tubular abnormalities that are likely to be involved in ischemic and toxic ARF. This information has led to impressive advances in the development of a number of different pharmacological interventions that are highly effective in ameliorating the renal dysfunction in animal models of ARF. Although these developments are exciting and promising, enthusiasm of investigators involved in this endeavor has been tempered somewhat by the results of a few recent clinical studies of patients with ATN. These trials, designed to examine the efficacy in humans of some of the interventions effective in animal models of ARF, have resulted in little or no benefit. This is therefore an important time to reevaluate the approaches we have taken over the past three to four decades to develop new and effective treatments for ATN in humans. The major goals of this review are 1) to evaluate the relevance and utility of the experimental models currently available to study ischemic and toxic renal injury, 2) to suggest novel experimental approaches and models that have the potential to provide advantages over methods currently available, 3) to discuss ways of integrating results obtained from different experimental models of acute renal injury and of evaluating the relevance of these findings to ATN in humans, and 4) to discuss the difficulties inherent in clinical studies of ATN and to suggest how studies should be best designed to overcome these problems.

Attenuation of cisplatin-induced acute renal failure is associated with less apoptotic cell death

To clarify the pathophysiologic role of apoptosis in acute renal failure (ARF), we examined whether the attenuation of cisplatin-induced ARF is associated with the change in the degree of apoptotic cell death. The administration of cisplatin (CDDP) (6 mg/kg body weight) in rats induced ARF at day 5, as manifested by a significant increase in serum creatinine (Scr) and tubular damage. CDDP-induced apoptotic cell death was confirmed by electron microscopic examination, agarose gel electrophoresis, and increased cells positive for TaT-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) in the outer medulla of the kidney. Treatment with dimethylthiourea (DMTU)--a scavenger of hydroxyl radicals--or glycine abrogated CDDP-induced increases in Scr, the tubular damage score, and the number of TUNEL-positive cells. Pretreatment with uranyl acetate (UA) induced a significant expression of Bcl-2 in the kidney and ameliorated CDDP-induced increases in Scr, the tubular damage score, and TUNEL-positive cells in the outer stripe of the outer medulla. Our findings indicate (1) that the attenuation of CDDP-induced ARF was associated with less apoptotic cell death and (2) that the induction of the anti-apoptotic protein Bcl-2 attenuated apoptosis and tubular damage. Our results suggest that apoptotic cell death may play an important role in the development of cisplatin-induced ARF.

Treatment of acute renal failure

Acute renal failure is a life threatening illness whose mortality has remained high since the introduction of hemodialysis 25 years ago, despite advances in supportive care. Acute renal failure is an extremely morbid and costly disorder with a significant proportion of patients progressing to end-stage renal disease requiring dialysis. To the nephrologist, acute renal failure remains an extremely frustrating disease, because the pathophysiology is not well understood and the limited therapeutic options force the nephrologist to sit on the sidelines and wait for renal function to return. For example, dialysis remains the only FDA-approved treatment for acute renal failure, but dialysis may also cause renal injury that prolongs renal failure. The purpose of this perspective is to understand the results of the recent, largely negative, clinical trials in view of recent advances in the epidemiology of ARF. This review will also discuss diagnostic tools, strategies for improved design of clinical trials, and other therapeutic interventions that will be needed to properly treat acute renal failure in the 21st century.

Impairment of cellular redox status and membrane protein activities in kidneys from rats with ischemic acute renal failure

Cellular redox status and membrane protein activities were analyzed in kidneys from rats with ischemic acute renal failure (ARF). ARF was induced by clamping the left renal artery for 50 min. A parallel group of control animals was processed. In the ischemic group urea plasma levels were statistically increased as compared with the control group. Studies employing whole kidney homogenates revealed that ischemia produces an increment in lipid peroxidation levels and a reduction in glutathione concentration and in superoxide dismutase and glutathione peroxidase activities. Since lipid peroxidation may alter the function of membrane proteins we determined succinate cytochrome c reductase (SuccR), sodium-potassium ATPase (Na-K-ATPase), glucose-6-phosphatase (G-6-Pase) and alkaline phosphatase (ALP) activities in whole renal homogenates. Only G-6-Pase and ALP activities were modified by ischemia. Since ALP is a brush border membrane (BBM) enzyme and BBM is one of the main target structures in ARF, we assessed some parameters of BBM functionality. ALP, gamma-glutamyl transferase (gamma-GT) and 5'-nucleotidase (5'-NT) showed diminished activities in BBM from ischemic kidneys. Ischemia also modified the Vmax of paraaminohippuric acid (PAH) uptake without altering Km. An increment of lipid peroxidation and membrane fluidity in BBM was observed after the treatment. Total membrane proteins and protein recoveries in BBM were similar in both experimental groups. Sialic acid and sulfhydryl levels were similar in BBM from ischemic kidney and control ones. In summary, ARF induced by renal artery clamping for 50 min takes place with a significant increase in urea plasma levels. A decrease in the antioxidant defense system is detected. This induces lipid peroxidation in whole renal tissue, which may justify the diminished activities of some membrane enzymes such as G-6-Pase and ALP. A specific analysis of BBM function reveals a significant increment of lipid peroxidation which may be the cause of an increased membrane fluidity. This latter parameter might be, at least in part, responsible for the damaged function of apical ALP, 5'-NT, gamma-GT and PAH carrier.