Ischemic Acute Renal Failure In Rats Research Articles

Protective Effect of Agmatine on Ischemia/Reperfusion-induced Renal Injury in Rats

Enhanced renal sympathetic nerve activity (RSNA) during ischemic period and the renal venous norepinephrine (NE) overflow after reperfusion play important roles in the development of ischemic/reperfusion (I/R)-induced acute renal failure (ARF) in rats. This study evaluated whether agmatine, which is known to reduce sympathetic nerve activity and NE overflow by electrical stimulation, would prevent the I/R-induced renal dysfunction. Ischemic ARF was induced by clamping the left renal artery and vein for 45 minutes followed by reperfusion 2 weeks after the contralateral nephrectomy. Intravenous (IV) injection of agmatine (100 and 300 micromol/kg) to ischemic ARF rats dose-dependently suppressed the enhanced RSNA and attenuated the I/R-induced renal dysfunction and histological damage. Intracerebroventricular (ICV) injection of agmatine (600 nmol/kg) to ischemic ARF rats suppressed the enhanced RSNA during the ischemic period and attenuated the I/R-induced renal injury. Furthermore, both IV and ICV injection of agmatine significantly suppressed the renal venous NE overflow after the reperfusion. These results indicate that agmatine prevents the development of I/R-induced renal injury, and the effect is accompanied by suppression of the enhanced RSNA during ischemic period and NE overflow from renal sympathetic nerve endings.

Heat Preconditioning Attenuates Renal Injury in Ischemic ARF in Rats

Although heat preconditioning has been known to be protective in various types of injury, the precise molecular mechanism for this is unclear. Recent observations that indicate that previous heat shock has an anti-inflammatory, antiapoptotic effect led to this investigation of the in vivo effect of heat preconditioning on NF-kappaB activation and inflammation and also on tubular cell injury in ischemic acute renal failure (ARF). Heat preconditioning provided marked functional protection and also reduced histologic evidence of tubular necrosis. Ischemia/reperfusion-induced NF-kappaB activation was suppressed by heat preconditioning with a subsequent decrease in monocyte chemoattractant protein-1 expression and inflammatory cell infiltration. Heat preconditioning also suppressed the accumulation of phosphorylated inhibitory kappaBalpha (IkappaBalpha) with a resultant depletion of cytoplasmic IkappaBalpha, indicating that heat preconditioning blocked the activation of the IkappaB kinase complex. Tubular cell apoptosis, determined by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, also was decreased by heat preconditioning, and this was accompanied by decreased caspase 3 activation. Among several heat-shock proteins (HSP), HSP-70 was induced primarily by heat preconditioning. Inhibition of HSP-70 by quercetin almost completely reversed the functional protection that was provided by heat preconditioning. These data provide evidence that HSP-70 affords protection via inhibition of NF-kappaB-mediated inflammation and also inhibition of the cell death pathway in ischemic ARF. Further elucidation of the cytoprotective mechanism of stress proteins could facilitate new target or drug development in the treatment of ARF.

Renoprotective Effects of l-Carnosine on Ischemia/Reperfusion-Induced Renal Injury in Rats

We examined the renoprotective effects of l-carnosine (beta-alanyl-l-histidine) on ischemia/reperfusion (I/R)-induced acute renal failure (ARF) in rats. Ischemic ARF was induced by occlusion of the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. In vehicle (0.9% saline)-treated rats, renal sympathetic nerve activity (RSNA) was significantly augmented during the renal ischemia, and renal function was markedly decreased at 24 h after reperfusion. Intracerebroventricular injection of l-carnosine (1.5 and 5 pmol/rat) to ischemic ARF rats dose-dependently suppressed the augmented RSNA during ischemia and the renal injury at 24 h after reperfusion. N-alpha-Acetyl-l-carnosine [N-acetyl-beta-alanyl-l-histidine; 5 pmol/rat intracerebroventricular (i.c.v.)], which is resistant to enzymatic hydrolysis by carnosinase, did not affect the renal injury, and l-histidine (5 pmol/rat i.c.v.), a metabolite cleaved from l-carnosine by carnosinase, ameliorated the I/R-induced renal injury. Furthermore, a selective histamine H(3) receptor antagonist, thioperamide (30 nmol/rat i.c.v.) eliminated the preventing effects by l-carnosine (15 nmol/rat intravenously) on ischemic ARF. In contrast, a selective H(3) receptor agonist, R-alpha-methylhistamine (5 pmol/rat i.c.v.), prevented the I/R-induced renal injury as well as l-carnosine (5 pmol/rat) did. These results indicate that l-carnosine prevents the development of I/R-induced renal injury, and the effect is accompanied by suppressing the enhanced RSNA during ischemia. In addition, the present findings suggest that the renoprotective effect of l-carnosine on ischemic ARF is induced by its conversion to l-histidine and l-histamine and is mediated through the activation of histamine H(3) receptors in the central nervous system.

Paracrine and differentiation mechanisms underlying stem cell therapy for the damaged kidney

NATIVE KIDNEY ACUTE RENAL FAILURE (ARF) occurs in 2‐5% of hospitalized patients and is associated with high mortality (11). Allograft ARF occurs in 30‐50% of deceased donor kidney transplants and leads to longer hospital stays, a higher incidence of acute rejection, and reduced long-term graft survival (13). There is no specific therapy for ARF except for supportive care. A surge of evidence over the last decade supports an important role for inflammatory mediators, microvascular dysfunction, and apoptosis in the pathogenesis of the injury and extension phase of ARF (12). The mechanisms of recovery, less well understood, are felt to include a recapitulation of mechanisms originally involved in renal development. It is commonly believed that kidney progenitor cells, from either the kidney or an extrarenal source, repopulate the kidney during the recovery phase of ARF and drive the repair process (9). A popular model was that damaged/dead cells are removed and the kidney stem cells migrate to necrotic areas, differentiate, and repopulate the kidney. Indeed, injured human kidney transplants from female donors into male recipients were found to have Y chromosome staining of tubular epithelial cells, demonstrating that they were of recipient origin (5). In support of this model are studies in mice in which labeled bone marrow was tracked with -galactosidase (-gal) staining into postischemic kidney. -Gal staining was observed in 20% of the proximal tubular cells at 1 wk after ischemia, and also to some extent within 48 h of ischemia (7). Despite the focus on stem cell effects on repair, mice without functional bone marrow in that study had a worse early course of ARF, suggesting that bone marrow-derived cells had an early protective effect on the injury process. In another murine study, male-derived cells were found in female mouse kidney recipients after ischemia (8). However, recent work has shown that -gal staining to identify differentiated stem cells has considerable limitations, false positive results can result from the kidney’s endogenous -gal, and the staining validity is vulnerable to slight pH shifts (3). In a cisplatin model of ARF, administration of mesenchymal stem cells improved kidney function and structure (10). Given that Y chromosome-containing cells were found in recipient tubular epithelium of female mice and expressed specific lectin-binding proteins found in proximal tubules, transdifferentiation was concluded to be the mechanism of enhanced repair. Administration of skeletal muscle-derived stem cells that were differentiated into endothelial cells provided early protection from ischemic ARF in mice and were detected in glomeruli and peritubular capillaries using green fluorescent protein detection (1).

Detection of inflammation following renal ischemia by magnetic resonance imaging

Determining the disease culprits in human acute renal failure (ARF) has been difficult because of the paucity of renal biopsies and the lack of noninvasive methods to determine the location or cause of renal injury. Recently, ultrasmall superparamagnetic iron oxide (USPIO) particles have been used to detect inflammation in animal models. Therefore, we tested if USPIO enhanced magnetic resonance imaging (MRI) could detect inflammation in ischemic ARF in rats. Rats were subjected to 40 or 60 minutes of bilateral ischemia or injected with mercuric chloride. MR images were obtained before and 24 hours after USPIO injection, and the signal intensity decrease in the outer medulla was measured. Cells containing iron particles were identified by iron staining and transmission electron microscopy (TEM). Leukocytes were identified by ED-1 and chloracetate esterase staining. Injection of USPIO particles caused a black band to appear in the outer medulla at 48, 72, and 120 hours after ischemia. This band was not detected in normal animals, 24 hours after ischemia, or 48 hours after mercuric chloride injection. The signal intensity change in the outer medulla correlated with serum creatinine and the number of iron particle containing cells. Most infiltrating cells were macrophages, and iron particles were present inside lysosomes of macrophages. USPIO injection did not alter renal function in normal or ischemic animals. USPIO-enhanced MRI could detect inflammation noninvasively from 48 hours after 40 or 60 minutes of renal ischemia in rats. This method might be useful to understand the pathogenesis of human ARF and to evaluate the effectiveness of anti-inflammatory agents.

Tin chloride pretreatment prevents renal injury in rats with ischemic acute renal failure.

To investigate whether tin chloride pretreatment ameliorates renal injury in rats with ischemic acute renal failure (IARF) by virtue of its kidney-specific heme oxygenase-1 induction. Randomized, masked, controlled animal study. University-based animal research facility. Sprague-Dawley male rats, weighing 200-230 g (n = 359). Rats were injected with tin chloride subcutaneously, because subcutaneous administration of tin chloride is known to specifically and potently induce renal heme oxygenase activity in the rat. Anesthetized rats were subjected to bilateral flank incisions, and the right kidney was removed. Renal ischemia for 40 mins was performed by left renal microvascular clamping, followed by reflow of the blood. Tin chloride treatment specifically induced heme oxygenase-1 mRNA and protein in the proximal tubular epithelial cells of the kidney without apparent cell injury in the rat. Tin chloride treatment before renal ischemia augmented the induction of heme oxygenase-1 in IARF rats at both transcriptional and protein concentrations in the renal epithelial cells compared with IARF animals. Tin chloride pretreatment, which decreased microsomal heme concentration, ameliorated the ischemic renal injury as judged by the significant decrease in serum creatinine and blood urea nitrogen concentrations and the lesser tubular epithelial cell injuries. In contrast, inhibition of heme oxygenase activity by treatment with tin mesoporphyrin, which increased microsomal heme concentration, abolished the beneficial effect of tin chloride pretreatment. These findings indicate that tin chloride pretreatment significantly ameliorates renal injury in rats with IARF by virtue of its specific heme oxygenase-1 induction in renal epithelial cells. These findings also suggest that heme oxygenase-1 induction plays an important role in protecting renal cells from oxidative damage caused by heme.

COMPARISON OF THE FAT ELIMINATION BETWEEN LONG-CHAIN TRIGLYCERIDES AND MEDIUM-CHAIN TRIGLYCERIDES IN RATS WITH ISCHEMIC ACUTE RENAL FAILURE

To guide the administration of fat emulsion in the nutritional support of acute renal failure (ARF), pharmacokinetic analysis with an one-compartment open model after bolus intravenous injection was performed to compare the elimination kinetics of long-chain triglycerides (LCT) and medium-chain triglycerides (MCT) in ischemic acute renal failure rats. Sprague-Dawley rats were randomized into four groups, namely LCT normal group, LCT ARF group, MCT normal group and MCT ARF group. The model of ischemic acute renal failure was induced by clamping the left renal artery for 60 min and contralateral nephrectomy. All the rats were fasted with water ad libitum for 10 h before 0.3 g/kg body weight of 10% Intralipid (LCT) or 10% Lipofundin (MCT:LCT = 50:50) was injected as a bolus to them via the tail vein. The serum triglyceride concentration was determined at 2, 10, 40, 70, 100, 130 and 160 min after intravenous injection for kinetic analysis. The results showed that the elimination rate constant (ke) of LCT ARF group was significantly decreased, while the half life period (t1/2) of it was significantly longer than those of LCT normal group. The ke and t1/2 of MCT showed no statistical difference between normal and ARF groups. In the normal group the ke of LCT was significantly decreased compared with MCT whereas the t1/2 was significantly prolonged. In the ARF group the ke of LCT was much less than that of MCT while the t1/2 was much longer. The serum insulin levels of both MCT groups were significantly higher than those of LCT groups. These results indicate that MCT will be eliminated more rapidly than LCT in ARF rats. MCT may also increase the secretion of insulin. In conclusion, MCT may be more favorable than LCT in the nutritional management of ARF.

Proteasome Inhibition Attenuates Renal Endothelin-1 Production and the Development of Ischemic Acute Renal Failure in Rats

Summary: The objectives of this study were (1) to assess the role of a proteasome-dependent proteolytic pathway in the pathogenesis of acute renal failure (ARF) induced by ischemia-reperfusion, and (2) to determine the involvement of this proteolytic pathway in the enhanced production of renal endothelin-1 (ET-1) in this model of ARF. ARF was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow, urinary osmolality and fractional excretion of sodium were measured to test the effectiveness of drugs used. Renal function in untreated ARF rats markedly decreased at 24 h after reperfusion. In addition, a marked increase in renal ET-1 content was evident in the ARF rats, compared to the sham-operated rats. Intraperitoneal injection of a proteasome inhibitor (PSI), N-benzyloxycarbony1-Ile-Glu(O-t-Bu)-Ala-leucinal, at a dose of 1 mg/kg, 1 h before the clamping, significantly attenuated the renal function impairment in the ischemic ARF rats, and the effect was accompanied by a decrease in renal ET-1 content. On the other hand, a calpain inhibitor, calpeptin, had little effect at the same dose. These results suggest that a proteasome-dependent proteolytic pathway is involved in the enhanced production of ET-1 in the kidney and the consequent renal functional damage in ischemic ARF.

Proteasome inhibition attenuates renal endothelin-1 production and the development of ischemic acute renal failure in rats.

The objectives of this study were (1) to assess the role of a proteasome-dependent proteolytic pathway in the pathogenesis of acute renal failure (ARF) induced by ischemia-reperfusion, and (2) to determine the involvement of this proteolytic pathway in the enhanced production of renal endothelin-1 (ET-1) in this model of ARF. ARF was induced by clamping the left renal artery and vein for 45 min followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function parameters such as blood urea nitrogen, plasma creatinine, creatinine clearance, urine flow, urinary osmolality and fractional excretion of sodium were measured to test the effectiveness of drugs used. Renal function in untreated ARF rats markedly decreased at 24 h after reperfusion. In addition, a marked increase in renal ET-1 content was evident in the ARF rats, compared to the sham-operated rats. Intraperitoneal injection of a proteasome inhibitor (PSI), N-benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal, at a dose of 1 mg/kg, 1 h before the clamping, significantly attenuated the renal function impairment in the ischemic ARF rats, and the effect was accompanied by a decrease in renal ET-1 content. On the other hand, a calpain inhibitor, calpeptin, had little effect at the same dose. These results suggest that a proteasome-dependent proteolytic pathway is involved in the enhanced production of ET-1 in the kidney and the consequent renal functional damage in ischemic ARF.

ラット虚血急性腎不全に対するレシチン化ｓｕｐｅｒｏｘｉｄｅ ｄｉｓｍｕｔａｓｅ （Ｌｅｃｉｔｈｉｎｉｚｅｄ ＳＯＤ， ＰＣ‐ＳＯＤ）の抑制効果

The pharmacological effect of lecithinized superoxide dismutase(PC-SOD) was evaluated using rat acute renal failure(ARF) model induced by ischemia-reperfusion. When PC-SOD was injected intravenously to rats 1 hr prior to ischemia, the increased plasma creatinine and BUN levels at 24 hr after reperfusion were significantly reduced. Treatment of PC-SOD immediately after reperfusion also reduced both of the increased ones. In while, inactivated PC-SOD(apo PC-SOD) did not show such effects at all. Unmodified SOD(U SOD) decreased the elevated plasma creatinine and BUN levels, but there was no significant difference. Renal SOD activity in ischemic ARF rats was significantly decreased, while renal myeloperoxidase(MPO) activity, a parameter of local infiltration of neutrophils was increased. The distribution study in ischemic ARF rats revealed that [3H] PC-SOD persisted much longer in the blood stream, while fewer amounts were detected in the kidney organ than those of [3H] U-SOD. The elevated renal MPO activity was significantly suppressed by PC-SOD. These results suggest that PC-SOD protected kidney injury in ischemic ARF rats by scavenging O2- on the cell membrane followed by inhibiting neutrophils infiltration.

Uninephrectomy reduces apoptotic cell death and enhances renal tubular cell regeneration in ischemic ARF in rats.

Contralateral uninephrectomy attenuates unilateral ischemic renal injury functionally and morphologically. In this study we investigated the effects of uninephrectomy on apoptotic renal cell death and tubular regeneration in ischemic acute renal failure (ARF) in rats. Unilateral ischemic injury was provoked by a 60-min left renal artery occlusion in right-nephrectomized (Nx) and sham-nephrectomized (sham-Nx) rats. Uninephrectomy attenuated tubular damage 48 h following the renal ischemia Apoptotic cells were found in renal tissue as early as 3 h after reperfusion and increased in number by 12 h. The "ladder" pattern of DNA fragments on agarose gel electrophoresis was also apparent in ischemic kidney. Uninephrectomy reduced apoptotic cells and DNA fragmentation. The expression of proliferating cell nuclear antigen (PCNA) could be seen 24 h after reperfusion and progressively increased thereafter PCNA expression in ischemic kidney was greater in Nx than sham-Nx rats at 24 h after renal reperfusion. These data suggest that uninephrectomy reduces apoptotic cells and DNA fragmentation and enhances PCNA expression. The reduced apoptotic cell death and enhanced cell regeneration may be importantly involved in the uninephrectomy-induced attenuation of ischemic acute renal failure in rats.

Recombinant human insulin-like growth factor-I accelerates recovery and reduces catabolism in rats with ischemic acute renal failure.

This study evaluated whether recombinant human insulin-like growth factor-I (rhIGF-I) enhances recovery of renal function and reduces catabolism in rats with ischemic acute renal failure (ARF). ARF and sham rats received subcutaneous injections of either rhIGF-I or vehicle three times daily starting 5 h after surgery. Serum creatinine and urea, which initially rose similarly in the ARF+vehicle and ARF+rhIGF-I rats, increased more slowly after commencing the rhIGF-I injections. 72 h after surgery, the ARF+rhIGF-I rats, in comparison with ARF+vehicle animals, showed significantly greater renal plasma flow and filtration fraction, a fivefold higher glomerular filtration rate, greater renal cortical IGF-I levels, increased proliferating cell nuclear antigen expression in proximal tubule nuclei and enhanced DNA synthesis in the renal cortex, corticomedullary junction, glomeruli, and tubules as demonstrated by [3H]thymidine incorporation and in corticomedullary junction tubules as determined by autoradiography. Estimated total nitrogen output (ETNO) was greater in ARF+vehicle than in ARF+rhIGF-I or sham rats throughout the study. ETNO in ARF+rhIGF-I rats returned to sham values by the second day after surgery. 72 h after surgery, protein degradation was increased and protein synthesis reduced in the epitrochlearis muscle of ARF+vehicle as compared with ARF+rhIGF-I or sham+vehicle rats. Thus, treatment with rhIGF-I starting 5 h after inducing ischemic ARF in rats increases recovery of renal function, enhances formation of new renal tubular cells, lowers protein degradation, and increases protein synthesis in skeletal muscle and reduces net catabolism.

Smooth muscle calcium and endothelium-derived relaxing factor in the abnormal vascular responses of acute renal failure.

Abnormal renovascular reactivity, characterized by paradoxical vasoconstriction to a reduction in renal perfusion pressure (RPP) in the autoregulatory range, increased sensitivity to renal nerve stimulation (RNS), and loss of vasodilatation to acetylcholine have all been demonstrated in ischemic acute renal failure (ARF). To determine if ischemic injury alters vascular contractility by increasing smooth muscle cell calcium or calcium influx, the renal blood flow (RBF) response to reductions in RPP within the autoregulatory range and to RNS were tested before and after a 90-min intrarenal infusion of verapamil or diltiazem in 7-d ischemic ARF rats. Both calcium entry blockers, verapamil and diltiazem, blocked the aberrant vasoconstrictor response to a reduction in RPP and RNS (both P less than 0.001). In a second series of experiments the potential role of an ischemia-induced endothelial injury and of the absence of endothelium-derived relaxing factor (EDRF) production were examined to explain the lack of vasodilatation to acetylcholine. Acetylcholine, bradykinin (a second EDRF-dependent vasodilator), or prostacyclin, an EDRF-independent vasodilator, was infused intrarenally for 90 min, and RBF responses to a reduction in RPP and RNS were tested in 7-d ischemic ARF rats. Neither acetylcholine nor bradykinin caused vasodilatation or altered the slope of the relationship between RBF and RPP. By contrast, prostacyclin increased RBF (P less than 0.001), but did not change the vascular response to changes in RPP. It was concluded that the abnormal pressor sensitivity to a reduction in RPP and RNS was due to changes in renovascular smooth muscle cell calcium activity that could be blocked by calcium entry blockers. A lack of response to EDRF-dependent vasodilators, as a result of ischemic endothelial injury, may contribute to the increased pressor sensitivity of the renal vessels.