The regulation of ischemic acute renal failure by extrarenal organs

The Peripheral Immune System and Traumatic Brain Injury: Insight into the role of T-helper cells

Emerging evidence suggests that immune-inflammatory processes are key elements in the physiopathological events associated with traumatic brain injury (TBI). TBI is followed by T-cell-specific immunological changes involving several subsets of T-helper cells and the cytokines they produce; these processes can have opposite effects depending on the disease course and cytokine concentrations. Efforts are underway to identify the T-helper cells and cytokine profiles associated with prognosis. These predictors may eventually serve as effective treatment targets to decrease morbidity and mortality and to improve the management of TBI patients. Here, we review the immunological response to TBI, the possible molecular mechanisms of this response, and therapeutic strategies to address it.

Effects of different periods of gastric ischemia on liver as a remote organ1

PURPOSE

To evaluate the hepatic changes associated with gastric ischemia.

METHODS

Thirty male rabbits were studied, distributed in 3 groups (n=10). Group 1: ligature and section of the gastric vasculature and removal of the liver after three hours; Group 2: ligature and section of the gastric vasculature and removal of the liver after 6 hours; Group 3: ligature and section of the gastric vasculature and removal of the liver after 12 hours. Blood samples were collected immediately before surgery and after the determined time of ischemia in each group to evaluate the hepatic function. After the death of the rabbits, the liver was removed for macro and microscopic study.

RESULTS

An increase in aminotransferases and bilirubin occurred in groups 2 and 3. Total protein and albumin diminished in all of the animals. All of the rabbits from groups 2 and 3 presented hepatocellular necrosis.

CONCLUSION

The devascularization of the stomach for a period of above three hours is associated with hepatic morphological and functional disorders.

CVP and PAoP Measurements Are Discordant During Fluid Therapy After Traumatic Brain Injury

The objective of the study was to compare measurements of central venous pressure (CVP) and pulmonary artery occlusion pressures (PAoP) as estimates of intravascular volume during the first 96 hours of fluid therapy after traumatic brain injury (TBI). One thousand five hundred ten simultaneous CVP and PAoP measurements from 31 patients entered into the National Acute Brain Injury Study: Hypothermia (NABISH:H) protocol were retrospectively compared. The effect of fluid administration and body temperature upon the paired measurements was statistically assessed. Agreement between CVP and PAoP values was poor. The CVP and PAoP were equal in only 11% of paired values. The CVP was always higher than PAoP in 1 patient, whereas PAoP always exceeded the CVP in 5 others. In 74% of the pairs, the PAoP was higher than the CVP, whereas in 15%, CVP was greater than PAoP. For any CVP measurement, the PAoP was either 3 mm Hg above or below the CVP in 67% of the pairs and at least 5 mm Hg above or below the CVP in 21% of the pairs. In 21 (68%) patients, PAoP was= 5 mm Hg above CVP in more than 4 readings, a clinically important difference. Discordance was not attributed to the fluid administered or to the temperature protocol. Neurological outcome appears affected by the volume of fluid administration. However, during initial therapy, estimates of intravascular volume provided by the CVP and PAoP are discordant. Although documented in other clinical conditions, the disparity noted here after TBI has not been previously reported. Assessment of intravascular volume to avoid hypovolemia should utilize other measurement techniques.

Sevoflurane prevents liver inflammatory response induced by lung ischemia-reperfusion

BACKGROUND

Transplants cause ischemia-reperfusion (IR) injury that can affect distant organs. Liver is particularly sensitive to IR injury. The present randomized experimental study was designed to investigate a possible protective effect of sevoflurane against liver inflammatory response to lung IR in a lung upper lobe left autotransplant model.

METHODS

Two groups (sevoflurane and control) of eight swines each were submitted to upper lobe left lung autotransplant. Hypnotic maintenance was performed with sevoflurane 3% or propofol 8 to 10 mg/kg per hr until pneumonectomy was done; then propofol was used for all animals. Blood and liver samples were taken in four different moments: prepneumonectomy, prereperfusion, 10 min postreperfusion and 30 min postreperfusion to measure levels of interleukin (IL)-1β, IL-10, tumor necrosis factor (TNF)-α, monocyte chemotactic protein (MCP)-1, nuclear factor (NF)-κB, C-reactive protein, ferritin and caspase 3. Non-parametric test was used to find statistical meaning.

RESULTS

Lung IR markedly increased the expression of TNF-α, IL-1β, MCP-1, NF-κB and caspase activity in control livers compared with basal levels, whereas liver IL-10 expression decreased 10 and 30 min post-reperfusion. Sevoflurane significantly decreased TNF-α, IL-1β, MCP-1, NF-κB liver expression and caspase 3 activity. Sevoflurane also reverted the lung IR-induced decrease in IL-10 expression.

CONCLUSIONS

The present results indicate that lung IR caused hepatic injury. Sevoflurane attenuated liver injury in a model of upper lobe left lung autotransplant in pigs.

Acute kidney injury: the beginning of the end of the dark ages

There has been enormous progress in the understanding of acute kidney injury (AKI) over the past 5 years. This article reviews some of the salient new findings, the challenges revealed by these findings and new insights into the pathogenesis of ischemic AKI. Clinical studies have demonstrated that even a small, transient rise in serum creatinine increases the risk of mortality in hospitalized patients and that a single event of AKI increases the risk for developing chronic kidney disease. Although the overall mortality rate from AKI has improved over the past 2 decades, it continues to be significant. Current treatment is focused on maintaining renal perfusion and avoiding volume overload. However, new therapeutic targets are emerging for the treatment of AKI as our understanding of the pathogenesis of ischemic injury and inflammation increases. Early diagnosis, however, continues to be challenging as the search continues for sensitive and specific biomarkers.

Gene polymorphisms of interleukin-10 and tumor necrosis factor-α are associated with contrast-induced nephropathy

BACKGROUND/AIMS

Contrast-induced nephropathy (CIN) is the third most common cause of hospital-acquired acute renal failure. However, the pathogenesis of CIN remains unclear. This study evaluated the role of anti-inflammatory cytokine interleukin-10 (IL-10) and pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) gene polymorphisms as CIN susceptibility markers after percutaneous coronary intervention (PCI).

METHODS

Four IL-10 tag SNPs (rs1554286, rs3021094, rs3790622, rs1800896) and three TNF-α tag SNPs (rs1799964, rs1800630, rs1800629) were analyzed by MALDI-TOF mass spectrometry in 53 CIN patients and 455 control subjects. Serum IL-10 and TNF-α were detected using ELISA.

RESULTS

When compared to controls, the CIN patients showed increased frequencies of CC (rs1554286) and AG+GG (rs1800896) genotypes in IL-10 and GA+AA (rs1800629) genotype in TNF-α (OR = 2.24 (1.13-4.44), p = 0.018; OR = 2.61 (1.30-5.26), p = 0.005, and OR = 2.11 (1.08-4.09), p = 0.025, respectively). Baseline serum IL-10 levels in CIN patients were significantly lower (1.02 ± 1.14 vs. 2.78 ± 4.73 pg/ml, p = 0.008). Patients with CIN had a higher rate of decline in renal function than those without CIN (0.89 ± 1.67 vs. 0.30 ± 0.95 ml/min/1.73 m(2) per month, p = 0.002). Significantly higher rates of decline in creatinine clearance were noted in patients with TNF-α (rs1800629) GA+AA than GG genotype (0.88 ± 1.83 vs. 0.36 ± 0.70, p = 0.03), and with IL-10 (rs1800896) AG+GG than AA genotype (1.28 ± 2.14 vs. 0.33 ± 0.90, p < 0.001).

CONCLUSIONS

Gene polymorphisms of IL-10 and TNF-α are associated with CIN risk and long-term renal outcome after PCI. More prospective studies are needed to confirm our results.

Ischaemic preconditioning prevents the liver inflammatory response to lung ischaemia/reperfusion in a swine lung autotransplant model

OBJECTIVES

Lung ischaemia/reperfusion (IR) induces a systemic inflammatory response that causes damage to remote organs. The liver is particularly sensitive to circulating inflammatory mediators that occur after IR of remote organs. Recently, remote ischaemic preconditioning has been proposed as a surgical tool to protect several organs from IR. The present study was designed to investigate a possible protective effect of lung ischaemic preconditioning (IP) against the liver inflammatory response to lung IR.

METHODS

Two groups [IP and control (CON)] of 10 Large White pigs underwent lung autotransplants (left pneumonectomy, ex situ cranial lobectomy and caudal lobe reimplantation). Before pneumonectomy was performed in the study group, IP was induced with two 5-min cycles of left pulmonary arterial occlusion and a 5-min interval of reperfusion between the two occlusions. Five animals underwent sham surgery. Liver biopsies were obtained during surgery at (i) prepneumonectomy, (ii) prereperfusion, (iii) 10 min after reperfusion of the implanted lobe and (iv) 30 min after reperfusion. The expression of tumor necrosis factor-α (TNF-α), interleukin (IL)-1, IL-10 and inducible form of nitric oxide synthase (iNOS) was analysed by western blotting. The expression of mRNA for TNF-α, IL1, IL-10, monocyte chemoattractant protein-1 (MCP-1), nuclear factor kappa beta and iNOS was analysed by reverse transcription-polymerase chain reaction. Caspase-3 activity was determined by enzyme-linked immunosorbent assay. Non-parametric tests were used to compare differences between and within groups.

RESULTS

Lung IR markedly increased expression of TNF-α (P = 0.0051) and IL-1 (P = 0.0051) and caspase-3 activity (P = 0.0043) in the CON group compared with the prepneumonectomy levels. A decrease of IL-10 mRNA expression was observed in the CON group after lung reperfusion. In the IP group, TNF-α (P = 0.0011) and IL-1 (P = 0.0001) expression and caspase-3 activity (P < 0.0009) were lower after reperfusion than in the CON group. IP caused reversion of the observed decrease of IL-10 mRNA expression (P = 0.016) induced in liver tissue by lung IR. Lung IR markedly increased the expression of mRNA MCP-1 after 10 min (P = 0.0051) and 30 min (P = 0.0051) of reperfusion. These increases were not observed in the IP or sham groups.

CONCLUSIONS

IP prevented liver injury induced by lung IR through the reduction of proinflammatory cytokines and hepatocyte apoptosis.

Cytokine production increases and cytokine clearance decreases in mice with bilateral nephrectomy

BACKGROUND

Serum cytokines are increased in patients with acute kidney injury (AKI) and predict increased mortality. It is widely assumed that increased renal production of cytokines is the source of increased serum cytokines; the role of extra-renal cytokine production and impaired renal cytokine clearance is less well studied. We hypothesized that cytokine production in AKI was mononuclear phagocyte dependent, independent of production by the kidneys, and that serum cytokine clearance would be impaired in AKI.

METHODS

Bilateral nephrectomy was used as a model of AKI to assess cytokine production independent of kidney cytokine production. Mononuclear phagocytes were depleted utilizing intravenous (IV) administration of liposome-encapsulated clodronate (LEC). Twenty-three serum cytokines were determined utilizing a multiplex cytokine kit. Proteins for cytokines were determined in the spleen and liver by enzyme-linked immunosorbent assay. Recombinant cytokines were injected by IV into mice with bilateral nephrectomy to determine the effect of absent kidney function on serum cytokine clearance.

RESULTS

Serum interleukin (IL)-6, chemokine (C-X-C motif) ligand 1 (CXCL1), IL-10, IL-1β, monocyte chemotactic protein 1 (MCP-1), IL-5 and eotaxin were increased in the serum of mice after bilateral nephrectomy and were reduced with LEC. Serum IL-12p40 and regulated upon activation, normal T-cell expressed, and secreted (RANTES) were increased after bilateral nephrectomy and were further increased with LEC. Spleen IL-6, CXCL1, IL-10 and IL-1β and liver IL-6 and IL-10 were increased after bilateral nephrectomy. After IV injection, IL-6, CXCL1, IL-10 and IL-1β had a prolonged serum cytokine appearance in mice with bilateral nephrectomy versus sham operation.

CONCLUSIONS

Increased mononuclear phagocyte production and impaired renal clearance contribute to serum cytokine accumulation in AKI, independent of kidney injury. The effect of AKI on cytokine production and clearance may contribute to the increased mortality of patients with AKI.

Effect of thymoquinone on hepatorenal dysfunction and alteration of CYP3A1 and spermidine/spermine N-1-acetyl-transferase gene expression induced by renal ischaemia-reperfusion in rats

OBJECTIVES

Renal ischaemia-reperfusion (I/R) is a well-characterised model of acute renal failure that causes both local and remote organ injury. The aim of this work was to investigate the effect of thymoquinone, the main constituent of the volatile oil extracted from Nigella sativa seeds, on renal and hepatic changes after renal ischaemia-reperfusion.

METHODS

Male Sprague-Dawley rats were divided into sham I/R vehicle-treated groups, and I/R thymoquinone-treated groups. Thymoquinone (10 mg/kg, p.o.) was administered for ten consecutive days to the I/R thymoquinone group before injury. I/R and I/R thymoquinone groups were subjected to 30-min ischaemia followed by 4-h reperfusion.

KEY FINDINGS

I/R resulted in a significant increase in malondialdehyde (MDA) level and decreases in glutathione-S-transferase (GST) and superoxide dismutase (SOD) activity in liver and kidney tissues. Thymoquinone treatment caused the reversal of I/R-induced changes in MDA as well as GST and SOD activity. Moreover, I/R caused a significant rise in creatinine and alanine aminotransferase serum levels. CYP3A1 mRNA expression was induced significantly by I/R in both liver and kidney tissues compared with sham group. Thymoquinone reduced significantly this increase. I/R caused induction of mRNA expression of spermidine/spermine N-1-acetyl-transferase (SSAT), a catabolic enzyme that participates in polyamine metabolism, in liver and kidney tissues. Thymoquinone reduced SSAT mRNA expression significantly in liver and markedly in kidney.

CONCLUSIONS

These findings suggested that thymoquinone protected against renal I/R-induced damage through an antioxidant mechanism as well as the decrease of CYP3A1 and SSAT gene expression.

Management of acute kidney injury in neurotrauma

Fortunately, the incidence of acute kidney injury (AKI) in neurotrauma is low and decreasing. Whereas the majority of AKI occurs in older patients with pre-existing chronic kidney disease, neurotrauma typically occurs in children and young adults with normal renal function. The development of outreach trauma teams has improved initial resuscitation, reducing both volume responsive and volume unresponsive cases of AKI. Most cases occur in the setting of multiple organ trauma with muscle injury, or patients who subsequently develop multiple organ failure. Once AKI has developed and renal replacement therapy is required, continuous modalities of renal replacement therapy offer an advantage to the patient with compromised cerebral perfusion and intracranial hypertension, by reducing the rate of change in serum urea, compared with standard intermittent therapies of hemodialysis and hemofiltration, thus minimizing abrupt changes in serum osmolality. Continuous hemodialysis and hemofiltration are better suited to maintain a normal or high serum sodium and thermal losses through the extracorporeal circuit, than peritoneal dialysis. Dialyzers should preferably be minimally bioincompatible and of a small surface area. In patients at risk of intracranial hemorrhage and those with invasive intracranial monitoring, systemic anticoagulants should either be avoided or regional anticoagulants should be used.

Improvement of cytokine response and survival time by bioartificial kidney therapy in acute uremic pigs with multi-organ dysfunction

OBJECTIVE

To explore whether bioartificial kidney (BAK) ameliorates cytokine response and biochemical indices, and prolongs the survival time in acute uremic pigs with multiple organ dysfunction syndrome (MODS).

METHODS

Hybridized pigs suffering from MODS and acute renal failure (ARF) were treated with BAK (Group A, n=6) or sham-BAK containing no cells (Group B, n=6), or received no treatment (Group C, n=5). Data on blood pressure, hepatic and renal function, IL-10, TNF-α, arterial blood gas, and survival time of all the pigs was recorded.

RESULTS

Mean arterial pressure (MAP, mmHg) responded more rapidly and reached higher values in Group A (91.82 ± 5.73) compared with Groups B and C at 24 hours (p<0.01). The peak level of serum IL-10 (pg/mL) in Group A (249.57 ± 43.51) was significantly higher than in Groups B and C (132.06 ± 17.53, 104.25 ± 13.42, p<0.01). Serum TNF-α level (pg/mL) in Group A dropped gradually to 402.91 ± 32.47 at 24 hours, and showed a significant discrepancy compared with those before treatment (537.16 ± 38.45) and Group B (512.94 ± 19.5, p<0.05). There was no difference in plasma endotoxin and serum IL-6 between pre-treatment and post-treatment in Groups A and B. BAK treatment, however, resulted in a significant decline in IL-6/IL-10 ratios. The average survival time (hours) in Group A (113.01 ± 14.32) was significantly longer, prolonged by 35.93% and 63.90% compared to Groups B and C (p<0.01), respectively.

CONCLUSIONS

The addition of renal tubule cell therapy to hemofiltration in an acutely uremic animal model with MODS altered systemic cytokine balance, ameliorated MAP, and prolonged survival time.

The bioartificial kidney in the treatment of acute kidney injury

Acute kidney injury (AKI) continues to have an exceedingly high mortality rate, despite advances in dialysis technology. Current dialysis therapies replace only the filtration function of the kidney, not the critical transport, metabolic, and endocrine functions of renal tubule cells. Replacement of these additional functions would provide more complete AKI therapy and thereby change the natural history of this disease process. A renal tubule assist device (RAD) containing living renal proximal tubule cells has been successfully engineered and has demonstrated differentiated absorptive, metabolic, and endocrine functions of normal kidney in vitro and ex vivo in animal experiments. The addition of the RAD containing human cells to conventional continuous renal replacement therapy has been shown in preclinical and clinical studies to have the potential to advance AKI treatment, from enhancing renal clearance to providing more complete renal replacement therapy. This "bioartificial kidney" demonstrates metabolic activity with systemic effects and improvement of survival in patients with AKI and multiorgan failure. It also appears to influence systemic leukocyte activation and the balance of inflammatory cytokines, suggesting that cell therapy by use of the RAD may improve morbidity and mortality by altering the proinflammatory state of patients with renal failure. In addition to providing cellular metabolic function, technologies directed toward disrupting systemic inflammatory response may well enhance the clinical outcome of critically ill patients in the future. Innovative approaches to intensive renal care such as the RAD may break the mold of current institutional dialysis therapies and provide numerous opportunities to develop lifesaving technologies.

Effects of different periods of renal ischemia on liver as a remote organ

AIM: To assess the hepatic changes after induction of different periods of renal ischemia.

METHODS: Rats were subjected to either sham operation or ischemia (30, 45 and 60 min) followed by 60 min reperfusion. Liver and renal functional indices were measured. Hepatic glutathione (GSH) and ferric reducing antioxidant power levels and the concentration of interleukin (IL)-10 and tumor necrosis factor (TNF-α) were evaluated. Portions of liver and kidney tissues were fixed for histological evaluation.

RESULTS: Forty-five minutes renal ischemia followed by 60 min reperfusion caused significant changes in liver structure and a significant reduction in renal function. These rats showed a significant decrease in liver GSH, as well as a significant increase in TNF-α and IL-10 concentrations. These results demonstrated that renal ischemia caused changes in liver histology, function, oxidative stress and inflammatory status, which led to a reduction in hepatic antioxidant capacity. With 30 min ischemia, the magnitude of these changes was less than those with 45 or 60 min ischemia.

CONCLUSION: A minimum of 45 min ischemia is needed to study the effects of renal injury on the liver as a remote organ.

The systemic inflammatory response after spinal cord injury damages lungs and kidneys

Spinal cord injury (SCI) triggers a well characterized, acute, local inflammation leading to secondary damage at the lesion site. Another little recognized problem may be the activation of circulating inflammatory cells that potentially damage tissues outside the cord. We investigated this problem using severe clip-compression SCI in rats. We studied systemic inflammation after SCI and its effects on lungs and kidneys, as dysfunction of these organs is a frequent, early complication after SCI. From 2-24 h after SCI, the number of circulating neutrophils (especially immature cells) significantly increased by 3-10 fold. Flow cytometry experiments revealed that SCI transiently activates these neutrophils, causing increased oxidative responses to phorbolmyristic acid at 2 h after SCI; then, from 4-24 h, the neutrophils were less responsive. Neutrophil longevity was increased (30-50% decrease in apoptosis) at 2-8 h after SCI. Immunohistochemical analyses demonstrated the invasion of neutrophils into lungs and kidneys (2 h-7 d after SCI) and more phagocytic macrophages in lungs (12 h, 3 d after SCI). Myeloperoxidase and matrix metalloproteinase-9 activity in lung and kidney homogenates increased (12 h-7 d after SCI). Expression of COX-2 increased and lipid peroxidation also occurred within this time. Control experiments inducing local cord damage by excitotoxic quisqualate injection verified that SCI per se is sufficient to trigger systemic inflammation and organ damage. In summary, SCI mobilizes and activates neutrophils that then migrate into visceral organs, a phenomenon occurring in parallel with their well-known entry into the cord injury site. The systemic inflammatory response to SCI should be targeted in the development of new therapeutic strategies to treat SCI.

Deficiency of heme oxygenase-1 impairs renal hemodynamics and exaggerates systemic inflammatory responses to renal ischemia

Heme oxygenase-1 may exert cytoprotective effects. In this study we examined the sensitivity of heme oxygenase-1 knockout (HO-1(-/-)) mice to renal ischemia by assessing glomerular filtration rate (GFR) and cytokine expression in the kidney, and inflammatory responses in the systemic circulation and in vital extrarenal organs. Four hours after renal ischemia, the GFR of HO-1(-/-) mice was much lower than that of wild-type mice in the absence of changes in renal blood flow or cardiac output. Eight hours after renal ischemia, there was a marked induction of interleukin-6 (IL-6) mRNA and its downstream signaling effector, phosphorylated signal transducer and activator of transcription 3 (pSTAT3), in the kidney, lung, and heart in HO-1(-/-) mice. Systemic levels of IL-6 were markedly and uniquely increased in HO-1(-/-) mice after ischemia as compared to wild-type mice. The administration of an antibody to IL-6 protected against the renal dysfunction and mortality observed in HO-1(-/-) mice following ischemia. We suggest that the exaggerated production of IL-6, occurring regionally and systemically following localized renal ischemia, in an HO-1-deficient state may underlie the heightened sensitivity observed in this setting.

Role of carbon monoxide and biliverdin in renal ischemia/reperfusion injury

Heme oxygenase (HO) isoforms catalyze the conversion of heme to carbon monoxide (CO) and biliverdin/bilirubin with a concurrent release of iron. There is strong evidence that HO activity and products play a major role in renoprotection, however the exact molecular mechanisms underlying the beneficial effects exerted by this pathway are not fully understood. This review is aimed at illustrating the possible mechanism/s by which HO is renoprotective in the context of ischemia/reperfusion. We will first analyze the effects of exogenous administration of bilirubin/biliverdin and CO and then describe their biological activities once generated endogenously following stimulation of the HO pathway by either pharmacological means or gene targeting-mediated approaches.

Acute renal failure: much more than a kidney disease

Acute renal failure is a frequent clinical problem with an increasing incidence, an unacceptably high mortality rate that has not improved in more than 40 years, and no specific treatment, yet renal failure is not the usual cause of death. The role of inflammation has been documented in both acute renal injury and cardiac dysfunction. Several investigators have shown that congestive heart failure is associated with increased mortality in patients with acute renal failure. This article reviews some of the cardiac and other distant organ effects of acute renal injury that may be important in the morbidity and mortality observed clinically. Cardiac changes after experimental renal ischemia include cytokine induction, leukocyte infiltration, cell death by apoptosis, and impaired function. I propose that the extrarenal effects of kidney injury must be considered in designing therapies. Acute renal failure has systemic consequences and must be thought of as more than a kidney disease.

Beneficial effects of MnTBAP, a broad-spectrum reactive species scavenger, in rat renal ischemia/reperfusion injury

BACKGROUND

In recent years, several lines of evidence have implicated reactive species as contributors to renal ischemia/reperfusion injury (I/R). This study was designed to investigate the effect of Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), a broad-spectrum reactive species scavenger, in the prevention of renal I/R injury.

METHODS

Experiments were performed on rats anesthetized with pentobarbital. After tracheotomy, the right femoral artery was cannulated and the mean arterial pressure and heart rate were recorded. A midline laparatomy was performed, and the renal arteries were carefully separated from surrounding tissues. After surgery and a stabilization period (60 min), the animals were randomly assigned to four groups: sham-operated; sham+MnTBAP; I/R; I/R+MnTBAP. In I/R groups, the rats were subjected to bilateral renal artery occlusion for 40 min followed by 6 h reperfusion. Other groups underwent the surgery protocol but did not undergo renal artery occlusion, and were maintained under anesthesia for the duration of the experiment. Rats were administered either MnTBAP (10 mg kg(-1), i.v. bolus, 15 min prior to I/R) or saline. Renal function was assessed by plasma creatinine (Cr), blood urea nitrogen (BUN), and aspartate aminotransferase (AST) measurements. The fractional excretion of Na(+) (FE(Na+)) and urinary N-acetyl-beta-D-glucosaminidase (NAG) activities were also measured. Renal section damage was evaluated by light microscopy, and oxidative stress status was evaluated by measurements of plasma and renal vitamin E levels.

RESULTS

We found that MnTBAP significantly reduced the I/R-mediated increases in plasma Cr, BUN, AST, FE(Na+), and NAG and improved the renal tissue histology.

CONCLUSION

Our results showed that MnTBAP was effective in preventing the development of I/R-induced renal injury.

Transgenic sickle mice are markedly sensitive to renal ischemia-reperfusion injury

Ischemic injury is invoked as a mechanism contributing to end-organ damage and other complications of sickle cell disease (SCD). However, the intrinsic sensitivity of tissues in SCD to ischemic insults has never been addressed. We examined the effect of renal ischemia in a transgenic mouse expressing human sickle hemoglobin. Twenty-four hours after bilateral, total renal artery occlusion for 15 minutes, transgenic sickle mice exhibited worse renal function and more marked histological injury. With bilateral renal ischemia of greater duration (22.5 minutes), and after 6 hours, transgenic sickle mice exhibited massive vascular congestion, sickling of red blood cells, more marked histological injury in the kidney, and more prominent congestion in the capillary beds in the lungs and heart. Additionally, serum amyloid P-component, the murine homologue of C-reactive protein, was markedly increased in transgenic sickle mice as compared to wild-type mice. Twenty-four hours after bilateral renal ischemia for 22.5 minutes, transgenic sickle mice exhibited 28% mortality, with no mortality observed in any other group. With bilateral renal ischemia of short or long duration, renal expression of caspase-3 was most prominent in transgenic sickle mice subjected to ischemia. Thus, renal ischemia in this murine model induces more severe renal injury and extrarenal complications. We conclude that tissues in SCD exhibit heightened vascular congestion and sensitivity to ischemia and that clinically apparent or silent episodes of ischemia may contribute to the complications of SCD.

Ischemia-reperfusion induces G-CSF gene expression by renal medullary thick ascending limb cells in vivo and in vitro

Ischemic acute renal failure involves not only the kidney but also extrarenal organs such as the bone marrow that produces inflammatory cells. By ELISA and RNase protection assays, we now show that renal ischemia-reperfusion increases serum concentrations of granulocyte macrophage colony-stimulating factor (G-CSF) protein and increases both G-CSF mRNA and protein in the ischemic kidney. In situ hybridization localized the increased G-CSF mRNA to tubule cells, including medullary thick ascending limb cells (mTAL), in the outer medulla. We also show that mTAL produce G-CSF protein and increase G-CSF mRNA after stimulation by reactive oxygen species in vitro. The production of G-CSF by the kidney after ischemia-reperfusion provides a means of communication from the injured kidney to the bone marrow. This supports the known inflammatory response to ischemia.

Acute Bile Duct Ligation Ameliorates Ischemic Renal Failure

BACKGROUND

Biliary obstruction affects the renal response to ischemia and also elicits a hepatic cytokine response. Using a murine model, we now test the hypothesis that these hepatic cytokines help determine the outcome of ischemic acute renal failure.

METHODS

C3H/HEN mice were subjected to bile duct ligation 24 h (ABDL) or 7 days (CBDL) prior to induction of acute ischemic renal failure (ARF). Serum creatinine (Scr), cytokine mRNA abundance, and renal histology were studied 24 h after renal ischemia.

RESULTS

ABDL prior to ARF resulted in amelioration of renal injury (Scr 0.7 +/- 0.1 mg/dl compared to 2.5 +/- 0.1 mg/dl in sham/ARF group, (mean +/- SE, n = 11/group). CBDL exacerbated renal injury. Increased hepatic mRNA for interleukin-10 (IL10) and interleukin-1 receptor antagonist (IL1RA) was detected in the ABDL/ARF group but not in the CBDL/ARF group. These data suggest that hepatic production of IL10 and IL1RA in response to ABDL ameliorates ischemic ARF, an effect that is lost after several days of BDL.

CONCLUSION

Our data support the concept that hepatic cytokines modulate renal injury. This adds a new dimension in our understanding of renal injury in the setting of hepatic disease.

Distant effects of experimental renal ischemia/reperfusion injury

Acute renal failure results in significant morbidity and mortality, yet renal failure is not the usual cause of death in the clinical situation. We have previously reported systemic increases in the inflammatory mediators tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1) after renal ischemia in the mouse. In the present study, an animal model of bilateral renal ischemia was used to test the hypothesis that cytokines released with renal ischemia have effects on other organ systems. Increased levels of immunoreactive TNF-alpha and IL-1 and intercellular adhesion molecule-1 mRNA were found in the heart after renal ischemia in the rat. This was accompanied by increases in myeloperoxidase activity, an index of tissue leukocyte infiltration, in the heart as well as the liver and lung. Functional changes in the heart 48 h after renal ischemia included increases in left ventricular end diastolic diameter, left ventricular end systolic diameter, and decreased fractional shortening by echocardiography. Evidence of apoptosis of cardiac cells was also found 48 h after an abbreviated period of renal ischemia insufficient to induce azotemia but not bilateral nephrectomy (which resulted in significant renal failure), suggesting that renal ischemia but not uremia is necessary for the apoptosis observed. It was also found that blocking the action of TNF-alpha limited cardiac apoptosis. Renal ischemia results in distant effects and the alterations observed in the heart may be important in the morbidity and mortality observed clinically.

Bioartificial kidney ameliorates gram-negative bacteria-induced septic shock in uremic animals

The bioartificial kidney (BAK) consists of a conventional hemofiltration cartridge in series with a renal tubule assist device (RAD) containing 10(9) porcine renal proximal tubule cells. BAK replaces filtration, transport, and metabolic and endocrinologic activities of a kidney. Previous work in an acutely uremic dog model demonstrated that BAK ameliorated endotoxin (lipopolysaccharide [LPS])-induced hypotension and altered plasma cytokine levels. To further assess the role of BAK in sepsis in acute renal failure, dogs were nephrectomized and 48 h later administered intraperitoneally with 30 x 10(10) bacteria/kg of E. coli. One hour after bacterial administration, animals were placed in a continuous venovenous hemofiltration circuit with either a sham RAD without cells (n = 6) or a RAD with cells (n = 6). BP, cardiac output, heart rate, pulmonary capillary wedge pressure, and systemic vascular resistance were measured throughout the study. All animals tested were in renal failure, with blood urea nitrogen and serum creatinine concentrations greater than 60 and 6 mg/dl, respectively. RAD treatment maintained significantly better cardiovascular performance, as determined by arterial BP (P < 0.05) and cardiac output (P < 0.02), for longer periods than sham RAD therapy. Consistently, all sham RAD-treated animals, except one, expired within 2 to 9 h after bacterial administration, whereas all RAD-treated animals survived more than 10 h. Plasma levels of TNF-alpha, IL-10, and C-reactive protein (CRP) were measured during cell RAD and sham RAD treatment. IL-10 levels were significantly higher (P < 0.01) during the entire treatment interval in the RAD animals compared with sham controls. These data demonstrated in a pilot large animal experiment that the BAK with RAD altered plasma cytokine levels in acutely uremic animals with septic shock. This change was associated with improved cardiovascular performance and increased survival time. These results demonstrate that the addition of cell therapy to hemofiltration in an acutely uremic animal model with septic shock ameliorates cardiovascular dysfunction, alters systemic cytokine balance, and improves survival time.