Ischemia-reperfusion injury of rat kidney relates more to tubular than to microcirculatory disturbances

Bovine polymerized hemoglobin (hemoglobin-based oxygen carrier-201) resuscitation in three swine models of hemorrhagic shock with militarily relevant delayed evacuation--effects on histopathology and organ function

OBJECTIVE

To test our hypothesis that hemoglobin-based oxygen carrier (HBOC)-201 resuscitation in hemorrhagic shock (HS) will not lead to increased organ injury and dysfunction.

DESIGN

Three swine HS models simulating military-relevant delayed evacuation: a) moderate controlled HS, b) severe controlled HS, and c) severe uncontrolled HS.

SETTING

Military research laboratory.

SUBJECTS

Swine.

INTERVENTIONS

Swine were anesthetized/intubated and instrumented. To induce HS, in two controlled hemorrhage experiments, 40% (moderate controlled HS) or 55% (severe controlled HS) of blood volume was withdrawn; in an uncontrolled HS experiment, the liver was crushed/lacerated. During a 4-hr "prehospital phase," pigs were resuscitated with HBOC-201 (HBOC) or Hextend (HEX) or were nonresuscitated (NON). Upon "hospital arrival," liver injury was repaired (severe uncontrolled HS), blood or saline was infused, hemodynamics were monitored, and blood was collected. Upon animal death and/or 72 hrs, necropsy was followed by histopathologic evaluation of organ injury (hematoxylin and eosin, electron microscopy) and immunohistochemistry of oxidative potential (3-nitrotyrosine). Significance (p < .05) was assessed by Kruskal-Wallis, analysis of variance/Bonferroni, and mixed procedure tests.

MEASUREMENTS AND MAIN RESULTS

Survival was significantly higher with HBOC than HEX only with severe uncontrolled HS (p = .002). Myocardial necrosis/fibroplasia, fluid requirements, cardiac output, and cardiac enzymes were generally similar or lower in HBOC than HEX pigs, but creatine kinase-MB (but not creatine kinase-MB/creatine kinase ratio) was higher with HBOC in moderate controlled HS. Alveolar/interstitial pulmonary edema was similar with HBOC and HEX, but Po2 was higher with HBOC in severe uncontrolled HS. Jejunal villar epithelial and hepatocellular necrosis were similarly minimal to moderate in all groups. Minimal biliary changes occurred exclusively with HBOC. Aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase were generally higher with HBOC than HEX. Mild renal papillary injury occurred more frequently with HBOC, but consistent patterns for urine output, blood urea nitrogen, and creatinine, were not seen. The 3-nitrotyrosine staining intensity was not different.

CONCLUSIONS

In comparison with hetastarch, HBOC-201 resuscitation of swine with HS increased survival (with severe HS), did not increase evidence of oxidative potential, and had histopathologic and/or functional effects on organs that were clinically equivocal (myocardium, lungs, hepatic parenchyma, jejunum, and renal cortex/medulla) and potentially adverse (hepatobiliary and renal papilla). The effects of HBOC-201-resuscitation in HS should be corroborated in controlled clinical trials.

Effects of whole blood, crystalloid, and colloid resuscitation of hemorrhagic shock on renal damage in rats: an ultrastructural study

PURPOSE

The aim of this study was to determine the effects of whole blood, crystalloid, and colloid treatment on histopathologic damage of kidney induced by hemorrhagic shock in rats.

METHODS

Fifty-six male Sprague Dawley rats were divided into 8 groups. The carotid artery was cannulated, and systolic arterial pressure (SAP), diastolic arterial pressure (DAP), heart rate (HR), and rectal temperature (RT) were observed during the procedure. The jugular vein also was cannulated, and the SAP was decreased by aspiration of 75% of blood through the jugular vein in the control (nonresuscitated) and study (resuscitated) groups, whereas blood was not diminished in the sham group. The hemorrhagic shock was permitted to last 45 minutes; then, the study group rats were resuscitated with heparinized shed autologous whole blood (WB), normal saline (NS), Lactated Ringer's solution (LR), hydroxyethyl starch 6% (HES6), hydroxyethyl starch 10% (HES10), or dextran 40 (D40). Histopathologic evaluation was performed under light and electron microscope.

RESULTS

The RT, SAP, and DAP decreased, and HR increased significantly in the control and study groups during the shock period compared with those of sham group. After volume resuscitation, these parameters changed to preshock levels. Electron and light microscopic examinations of kidneys showed severe proximal tubular degeneration with moderate glomerular damage in the control group; moderate proximal tubular degeneration with mild glomerular damage in the NS, LR, HES6, and HES10 groups; and mild proximal tubular degeneration with no evidence of glomerular damage in the WB and D-40 groups.

CONCLUSIONS

The characteristic ultrastructural features of hemorrhagic shock appear to be severe tubular degeneration and mild to moderate changes in glomeruli. Resuscitation of hemorrhagic shock with whole blood or dextran 40 solution appears to be most favorable therapy in preventing ultrastructural renal damage in rats.

Protective effect of glycine on renal injury induced by ischemia-reperfusion in vivo

Although glycine prevents renal tubular cell injury in vitro, its effect in vivo is not clear. The purpose of this study was to investigate whether a bolus injection of glycine given before reperfusion plus continuous dietary supplementation afterward would reduce renal injury caused by ischemia-reperfusion. Female Sprague-Dawley rats received a semisynthetic powdered diet containing 5% glycine and 15% casein (glycine group) or 20% casein (control group). Two days later, renal ischemia was produced by cross-clamping the left renal vessels for 15 min, followed by reperfusion. The right kidney was removed before reperfusion. The postischemic glomerular filtration rate (GFR) showed that renal function was less impaired and recovered more quickly in rats receiving glycine. For example, at day 7, GFR in controls (0.31 +/- 0.03 ml x min(-1) x 100 g(-1)) was about one-half that of glycine-treated rats (0.61 +/- 0.06 ml x min(-1) x 100 g(-1), P < 0.05). Furthermore, tubular injury and cast formation observed in controls was minimized by glycine (pathology score, 3.2 +/- 0.4 vs. 1.0 +/- 0.4, P < 0.05). Urinary lactate dehydrogenase (LDH) concentration was elevated by ischemia-reperfusion in the control group (260 +/- 22 U/l), but values were significantly lower by about fourfold (60 +/- 30 U/l) in glycine-fed rats. Similarly, free radical production in urine was significantly lower in glycine-treated animals. Importantly, on postischemic day 1, binding of pimonidazole, an in vivo hypoxia marker, was increased in the outer medulla in controls; however, this phenomenon was prevented by glycine. Two weeks later, mild leukocyte infiltration and interstitial fibrosis were still observed in controls, but not in kidneys from glycine-treated rats. In conclusion, these results indicate that administration of glycine indeed reduces mild ischemia-reperfusion injury in the kidney in vivo, in part by decreasing initial damage and preventing chronic hypoxia.

Different patterns of renal cell killing after warm and cold ischemia

Kidneys preserved for transplantation surgery sustain injuries caused by cold ischemia during storage. Additionally, kidneys harvested from non-heart-beating donors encounter the stress of warm ischemia. The aim of this study was to determine the specific cell types losing viability after warm and cold ischemia. In warm ischemia studies, the pedicles of left kidneys of Lewis rats were cross-clamped for up to 90 min. In cold ischemia studies, kidneys were flushed with cold University of Wisconsin solution and stored up to 48h at 0-1 degrees C. After warm or cold ischemia, kidneys were perfused via the renal arteries with Krebs-Henseleit bicarbonate (KHB) buffer at 37 degrees C, followed by trypan blue to label the nuclei of nonviable cells. Warm ischemia for 90 min caused renal failure and led to injury of proximal tubular cells, e.g., loss of brush borders, cast formation and trypan blue labeling. Cold ischemia for 48 h also caused renal failure but, unlike warm ischemia, caused trypan blue labeling of glomerular podocytes and peritubular endothelial cells. In warm ischemia-induced injury, electron microscopy showed shedding of microvilli and marked swelling of proximal tubular cells, microvilli and mitochondria. In cold ischemia-induced injury, podocytes were blebbed and swollen, and their pedicels were detached from the basement membrane, but disruption in proximal tubules was milder. In conclusion, warm ischemia triggers injury primarily to proximal tubular cells, whereas cold ischemia damages glomerular podocytes and peritubular endothelial cells in addition to proximal tubules.

Cu/Zn-superoxide dismutase gene attenuates ischemia-reperfusion injury in the rat kidney

Evidence has accumulated for a role of toxic oxygen radicals in the pathogenesis of ischemia-reperfusion injury in the kidney. The aim of this study was to evaluate the hypothesis that reducing postischemic renal injury is possible by delivery of the gene for the antioxidant enzyme superoxide dismutase (SOD). Female Sprague-Dawley rats received intravenous injections of recombinant adenovirus (1 x 10(9) pfu) containing the transgenes for Escherichia coli beta-galactosidase (Ad-LacZ, as control) or human Cu/Zn-SOD (Ad-SOD). Three days later, renal ischemia was produced by cross-clamping the left renal vessels for 60 min. The right kidney was removed before reperfusion and processed for the transgene. Renal SOD protein and activity in rats given Ad-SOD was 2.5-fold higher than from the animals receiving Ad-LACZ: Urinary lactate dehydrogenase concentrations were elevated by ischemia-reperfusion in the Ad-LacZ group (1403 +/- 112 U/L), yet values were 50% lower in Ad-SOD-treated rats. Free radical production was elevated by ischemia-reperfusion but was significantly lower in SOD-treated animals. Importantly, on postischemic day 1, glomerular filtration rates were reduced to 0.21 ml/min per 100 g in the Ad-LacZ group, whereas values remained significantly higher (0.39) in the Ad-SOD group. Two weeks after ischemia-reperfusion, inflammation, interstitial fibrosis, tubular atrophy and tissue levels of tumor necrosis factor alpha and interleukin-1 were significantly higher in the Ad-LacZ-treated than in Ad-SOD-treated rats. In conclusion, these results indicate that SOD expression can be increased by delivery of the sod gene to the kidney by intravenous injection and that sod gene transduction minimized ischemia-reperfusion-induced acute renal failure.

Ischaemic preconditioning ameliorates functional disturbance and impaired renal perfusion in rat ischaemia-reperfused kidneys

1. The effects of ischaemic preconditioning (IP) on renal function, haemodynamics and lipid peroxidation in the rat ischaemia-reperfused kidney model were examined. 2. In Wistar male rats, application of a single or three periods of 5 min bilateral renal ischaemia was performed prior to 30 min bilateral ischaemia and 90 min reperfusion (IR). The glomerular filtration rate (GFR) was estimated in terms of inulin clearance. Fractional excretion of sodium (FE(Na)) and lithium (FE(Li)), indicating total and proximal tubular sodium handling, respectively, was also measured and renal blood flow was monitored throughout the experiment. In addition, renal lipid peroxidation (LPO) levels in reperfused kidneys were evaluated. 3. A 2.8-fold increase in recovery of GFR (P < 0.005), a 50% reduction in FE(Na) (P < 0.005) and a 40% decrease in FE(Li) (P < 0.05) after IR resulted from the single period of 5 min IP. Renal blood flow was also higher than that in the control group (P < 0.01). No change of LPO levels was observed. 4. We conclude that IP may have an ability to ameliorate reperfused renal function and haemodynamics with a suitable period of preconditioned ischaemia, although this effect is independent of LPO.

Identification and kinetics of leukocytes after severe ischaemia/reperfusion renal injury

BACKGROUND

Leukocyte adhesion/infiltration in response to renal ischaemia/reperfusion (I/R) injury is a well-known but poorly understood phenomenon. The identification, kinetics, and exact role of these inflammatory cells in I/R injury and regeneration are still matters of debate.

METHODS

Uninephrectomized rats were submitted to 60 min renal ischaemia by clamping of renal vessels.

RESULTS

Severe acute renal failure was observed, with maximum functional impairment on day 2. By 12 h after the ischaemic event, up to 80% of proximal tubular cells in the outer stripe of outer medulla (OSOM) were already severely damaged. Proliferation (proliferating cell nuclear antigen (PCNA) staining) started after 24 h, reaching maximum activity on day 3. Regeneration of tubular morphology started on the 3rd day, and after 10 days 50% of tubules had regenerated completely. Interstitial leukocytes (OX-1 immunohistochemical staining) were already prominent at day 1, thereafter gradually increasing with time. The so-called neutrophil-specific identification methods (myeloperoxidase (MPO), chloroacetate esterase, mAb HIS-48) proved to be non-specific, since they also stained for macrophages, as demonstrated by flow cytometry and the combination of these stainings with the macrophage-specific ED-1 staining. MPO activity was already significantly increased at 1 h post-I/R (439+/-34%, P<0.005), reaching its maximum activity after 12 h of I/R (1159+/-138%, P<0.0005), declining thereafter. On the other hand, neutrophil presence investigated by H&E staining revealed only a few neutrophils in glomeruli, medullary rays, and OSOM at 24 h after the ischaemic event (4.7+/-4.2 cells/mm(2) vs controls=2.3+/-2.0 cells/mm(2) (n.s.)), and remained unchanged over the next 10 days. In contrast, significant monocyte/macrophage adhesion/infiltration (ED-1 staining) occurred at the OSOM at 24 h post-ischaemia (at 24 h, 120+/-46 cells/mm(2) vs. sham=18+/-4 cells/mm(2) (P<0.05)), became prominent at day 5 (1034+/-161 cells/mm(2) vs sham=18+/-18 cells/mm(2) (P<0.05)), and almost disappeared after 10 days. CD4(+) cells (W3/25) gradually increased from day 5, reaching a maximum at day 10. A few CD8(+) cells (OX-8) were apparent from days 3 until 10, but no B-cells (OX-33) were observed.

CONCLUSIONS

After severe warm I/R renal injury, a pronounced acute tubular necrosis occurs during the first 12-24 h in the absence of a marked cellular infiltrate, but with an important renal MPO activity, reflecting the activation of the adhering inflammatory cells (polymorphonuclear cells (PMNs) and mainly monocytes/macrophages). Only later at the time and site (OSOM) of regeneration a sequential accumulation of monocytes/macrophages and T cells becomes prominent, in contrast with the low number of neutrophils found in the kidney during the 10-day post-ischaemic period. The non-specificity of the so-called neutrophil-specific identification methods (MPO activity, naphthol AS-D chloroacetate esterase, or mAb HIS-48 staining), cross-reacting with monocytes/macrophages, explains the controversy in literature concerning the number of PMNs in post-ischaemic injury.

Effects of traditional versus delayed resuscitation on serum lactate and base deficit

OBJECTIVE

To test the hypothesis that delayed resuscitation of hemorrhagic shock produces a less severe shock insult than traditional resuscitation, characterized by repeated episodes of alternating hypotension and normotension.

METHODS

Female pigs were divided into three groups. Sham operated controls (C) (n = 4), sustained hypotension (SS) (n = 6), and hypotension with multiple cycles of shock and resuscitation (SR) (n = 6). SS and SR animals were bled to a mean arterial pressure (MAP) of 50 mmHg. SS animals were maintained at an MAP of 50 mmHg for 65 min and then resuscitated to baseline blood pressure with normal saline and shed blood. SR animals were initially bled and maintained at an MAP of 50 mmHg for 35 min, resuscitated to baseline BP, and subsequently bled and resuscitated twice more. The total period of shock was the same in both SS and SR.

RESULTS

Following hemorrhage, there was a significant increase in lactate and base deficit in SS as compared to C and SR.

CONCLUSION

Delayed resuscitation produces a more profound shock insult than traditional resuscitation.