Serum interleukin-18 levels are associated with nephropathy and atherosclerosis in Japanese patients with type 2 diabetes

OBJECTIVE

Interleukin (IL)-18 is a proinflammatory cytokine secreted from mononuclear cells. Serum concentration of IL-18 is a strong predictor of death in patients with cardiovascular diseases. Recent studies have shown that microinflammation is involved in the pathogenesis of diabetic nephropathy as well as of cardiovascular diseases. This study aimed to test the hypothesis that the serum level of IL-18 is a common predictor of nephropathy and atherosclerosis in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eighty-two Japanese patients with type 2 diabetes and 55 age- and sex-matched healthy control subjects were enrolled. Patients with renal dysfunction (creatinine clearance <1 ml/s) were excluded. We assessed clinical parameters and measured serum and urinary IL-18 levels, serum IL-6 levels, carotid intima-media thickness (IMT), and brachial-ankle pulse wave velocity (baPWV) in all patients. Further, we evaluated changes of urinary albumin excretion rate (AER) after 6 months in 76 diabetic patients.

RESULTS

Serum and urinary IL-18 levels were significantly elevated in patients with type 2 diabetes as compared with control subjects (serum IL-18 179 +/- 62 vs. 121 +/- 55 pg/ml, P < 0.001; urinary IL-18 97 +/- 159 vs. 47 +/- 54 pg/ml, P = 0.035). Univariate linear regression analysis showed significant positive correlations between serum IL-18 and AER (r [correlation coefficient] = 0.525, P < 0.001), HbA(1c) (r = 0.242, P = 0.029), high-sensitivity C-reactive protein (hs-CRP) (r = 0.240, P = 0.031), and urinary beta-2 microglobulin (r = 0.235, P = 0.036). Serum IL-18 levels also correlated positively with carotid IMT (r = 0.225, P = 0.042) and baPWV (r = 0.232, P = 0.040). We also found a significant correlation between urinary IL-18 and AER (r = 0.309, P = 0.005). Multivariate linear regression analysis showed that AER (standard correlation coefficients [B] = 0.405, P < 0.001) and hs-CRP (B = 0.207, P = 0.033) were independently associated with serum IL-18 levels. AER was also independently associated with urinary IL-18 levels (B = 0.295, P = 0.005). Moreover, serum and urinary IL-18 levels correlated positively with AER after 6 months (r = 0.489, P < 0.001 and r = 0.320, P = 0.005) and changes in AER during the follow-up period (r = 0.268, P = 0.018 and r = 0.234, P = 0.042).

CONCLUSIONS

Serum levels of IL-18 might be a predictor of progression of diabetic nephropathy as well as cardiovascular diseases.

Klotho reduces apoptosis in experimental ischaemic acute renal failure

BACKGROUND

Klotho is associated with the suppression of several ageing phenotypes. Because high klotho gene expression was detected in the kidney and several studies have found altered expression in animal models, we explored the physiological relevance of klotho expression in the kidney under renal ischemia reperfusion injury (IRI).

METHODS

Male Wistar rats were subjected to bilateral renal ischemia or sham operation, followed by reperfusion for 6, 12 or 24 h, or 2 to 10 days. Renal expression of klotho was assessed by real-time PCR or Western blotting. Creatinine levels were determined. Immunohistochemical studies and TUNEL staining were performed. An adenovirus harbouring the mouse klotho gene (ad-kl) was intravenously administered to one group of rats before renal IRI.

RESULTS

Renal klotho mRNA and protein expressions were significantly reduced in IRI rats the first day after ischemia. Pre-treatment with ad-kl resulted in a robust induction of klotho mRNA and protein in the liver but not in the kidney. Ad-kl gene transfer improved serum creatinine and the histological changes. Apoptosis induced by IRI was attenuated following ad-kl administration.

CONCLUSION

The data suggest klotho to be involved in the pathophysiology of IRI. Downregulation of renal klotho exacerbates ischaemic acute renal failure, and klotho gene induction has therapeutic potential in managing ischaemic renal damage.

Peripheral CD4 T-Cell Depletion Is Not Sufficient to Prevent Ischemic Acute Renal Failure

BACKGROUND

Ischemia reperfusion injury leading to acute renal failure (ARF) and delayed graft function is an important problem in organ transplantation. CD4+ T cells, essential for transplant rejection, may mediate ischemic ARF. We have demonstrated that the caspase-1 mediated production of IL-18 is pathogenic in ischemic ARF in mice. A potential source of IL-18 in ischemic ARF is the CD4+ T cell. We therefore examined the effect CD4+ T cell depletion on the development of ischemic ARF and the activation of IL-18.

METHODS

Functional and histological correlates were examined in two groups of mice with ischemic ARF: 1) CD4 T-cell depleted with the antibody GK1.5, and 2) T-cell receptor alpha-chain deficient (TCRalpha -/-) mice. TCRalpha -/- mice lack the alpha chain of the T-cell receptor and therefore lack functional CD4+ and CD8+ T cells.

RESULTS

Flow cytometry of lymph nodes and immunohistochemistry of kidneys demonstrated complete depletion of CD4+ T cells in mice with ischemic ARF treated with GK 1.5. CD4+ T-cell depletion did not confer functional (serum creatinine, BUN and FITC-labeled inulin clearance) or histological protection against ischemic ARF. Likewise, TCRalpha -/- mice were not protected against ischemic ARF. Renal caspase-1 activity and IL-18 protein were similar in CD4+ T-cell depleted and wild-type postischemic reperfusion.

CONCLUSIONS

Ischemic ARF can occur in the absence of classical T-cell function. The evaluation of other inflammatory mediators (e.g., macrophages or NK cells) as a source of IL-18 and mediator of ischemic ARF warrants further investigation.

A radical scavenger, edaravone, protects canine kidneys from ischemia-reperfusion injury after 72 hours of cold preservation and autotransplantation

BACKGROUND

Cold ischemia-reperfusion (I/R) injury is a prominent cause of delayed graft function after kidney transplantation. Reactive oxygen species play a crucial role in I/R injury. Edaravone is a synthetic radical scavenger that has been used in acute stroke. Some animal experiments have revealed its beneficial effects against I/R injury, but its effects after cold preservation and transplantation of canine kidneys are unknown.

METHODS

Female hybrid dogs weighing 11 to 13 kg were used. Under anesthesia, the left kidney was harvested. After 72 hr of preservation in cold histidine-tryptophan-ketoglutarate solution, autotransplantation was performed in the right iliac fossa, with contralateral nephrectomy. Animals were divided into control and treatment groups (n=6 per group). In the treatment group, edaravone was administered intravenously at harvest and at reperfusion (3 mg/kg) and in addition was added to the preservation solution (50 microM).

RESULTS

Animal survival at 2 weeks was four of six in the control group and six of six in the treatment group. Compared with controls, treated animals had higher mean urine output, higher mean glomerular filtration rate, improved tubular cell function, lower mean serum creatinine, and lower renal vascular resistance. Biopsy specimens from treated animals showed less tubular cell damage and decreased P-selectin expression in endothelial cells. Lipid peroxidation of renal tissue and urinary excretion of 8-hydroxy-2'-deoxyguanosine were suppressed by the treatment.

CONCLUSIONS

Edaravone reduced cold I/R injury in canine renal transplantation. The agent has the potential to ameliorate preservation injury in clinical transplantation.

Caspase inhibition reduces tubular apoptosis and proliferation and slows disease progression in polycystic kidney disease

We have previously demonstrated an increase in proapoptotic caspase-3 in the kidney of Han:SPRD rats with polycystic kidney disease (PKD). The aim of the present study was to determine the effect of caspase inhibition on tubular cell apoptosis and proliferation, cyst formation, and renal failure in the Han:SPRD rat model of PKD. Heterozygous (Cy/+) and littermate control (+/+) male rats were weaned at 3 weeks of age and then treated with the caspase inhibitor IDN-8050 (10 mg/kg per day) by means of an Alzet (Palo Alto, CA) minipump or vehicle [polyethylene glycol (PEG 300)] for 5 weeks. The two-kidney/total body weight ratio more than doubled in Cy/+ rats compared with +/+ rats. IDN-8050 significantly reduced the kidney enlargement by 44% and the cyst volume density by 29% in Cy/+ rats. Cy/+ rats with PKD have kidney failure as indicated by a significant increase in blood urea nitrogen. IDN-8050 significantly reduced the increase in blood urea nitrogen in the Cy/+ rats. The number of proliferating cell nuclear antigen-positive tubular cells and apoptotic tubular cells in non-cystic and cystic tubules was significantly reduced in IDN-8050-treated Cy/+ rats compared with vehicle-treated Cy/+ rats. On immunoblot, the active form of caspase-3 (20 kDa) was significantly decreased in IDN-8050-treated Cy/+ rats compared with vehicle-treated Cy/+ rats. In summary, in a rat model of PKD, caspase inhibition with IDN-8050 (i) decreases apoptosis and proliferation in cystic and noncystic tubules; (ii) inhibits renal enlargement and cystogenesis, and (iii) attenuates the loss of kidney function.

Caspase-1-deficient mice are protected against cisplatin-induced apoptosis and acute tubular necrosis

BACKGROUND

Cisplatin is a commonly used chemotherapeutic agent which causes apoptosis or necrosis of renal tubular epithelial cells in vitro. Caspases are a family of cysteine proteases that mediate apoptosis (caspase-3) and inflammation (caspase-1). Although well studied in vitro, caspases have not been previously studied in cisplatin-induced acute renal failure (ARF) in vivo.

METHODS

Cisplatin (30 mg/kg) was injected intraperitoneally into wild-type and caspase-1-deficient (-/-) C57BL/6 mice. Serum creatinine and blood urea nitrogen (BUN), and renal caspase-1, -3, -8 and -9 activity were measured on days 1, 2, and 3 after cisplatin injection. Kidneys were examined for acute tubular necrosis (ATN), neutrophils, and apoptosis on days 1, 2, and 3.

RESULTS

After cisplatin injection, serum creatinine and BUN were normal on day 1, began to increase on day 2, and peaked on day 3. Similarly, ATN scores and neutrophil counts peaked on day 3. In contrast, renal apoptosis significantly increased on day 2. Renal dysfunction, apoptosis, ATN scores and neutrophil infiltration were all reduced in the caspase-1(-/-) mice. In wild-type mice, caspase-1 and -3 activity increased on days 2 and 3. Caspase-3 activity was reduced by approximately 50% in caspase-1(-/-) mice; active caspase-3 detected by immunoblot was also reduced in caspase-1(-/-) mice. In vitro, addition of recombinant caspases to kidney cytosolic extracts determined that caspase-1 activates caspase-3 in renal tissue.

CONCLUSION

These results indicate that caspase-1 contributes to cisplatin-induced ARF and ATN (day 3). Furthermore, caspase-1 affects caspase-3 activation and apoptosis in cisplatin-induced ARF (day 2).

Molecular mechanisms of acute renal failure following ischemia/reperfusion

Acute renal failure (ARF) necessitating renal replacement therapy is a common problem associated with high morbidity and mortality in the critically ill. Hypotension, followed by resuscitation, is the most common etiologic factor, mimicked by ischemia/reperfusion (I/R) in animal models. Although knowledge of the pathophysiology of ARF in the course of this condition is increasingly detailed, the intracellular and molecular mechanisms leading to ARF are still incompletely understood. This review aims at describing the role of cellular events and signals, including collapse of the cytoskeleton, mitochondrial and nuclear changes, in mediating cell dysfunction, programmed cell death (apoptosis), necrosis and others. Insight into the molecular pathways in the various elements of the kidney, such as vascular endothelium and smooth muscle and tubular epithelium leading to cell damage upon I/R will, hopefully, open new therapeutic modalities, to mitigate the development of ARF after hypotensive episodes and to promote repair and resumption of renal function once ARF has developed.

Pathways of caspase-mediated apoptosis in autosomal-dominant polycystic kidney disease (ADPKD)

BACKGROUND

We have recently demonstrated an increase in apoptosis in Han:SPRD rat kidneys with autosomal-dominant polycystic kidney disease (ADPKD). Caspase-3 and caspase-7 are major mediators of apoptosis. There are two pathways of caspase-3 and caspase-7-mediated apoptosis: (1) the "extrinsic" pathway involving the death receptor Fas, Fas ligand (FasL), and caspase-8 and (2) the "mitochondrial" or "intrinsic" pathway involving Bcl-2 proteins, caspase-2, cytochrome c release, and caspase-9. The aim of the present study was to investigate the pathways of apoptosis in 3-week-old Han:SPRD rats with ADPKD.

METHODS

Fluorescent substrates were used to measure caspase activity. mRNA and protein was determined by ribonuclease protection assays and immunoblotting, respectively. The effect of caspase inhibitors on caspase activity in polycystic kidneys was determined.

RESULTS

Caspase-3 and caspase-7 activity was more than 100% increased in homozygous (Cy/Cy) compared to heterozygous (Cy/+) and normal littermate control (+/+) kidneys. Ribonuclease protection assays demonstrated no difference in caspase-3 mRNA. On immunoblotting, there was an increase in the proform of caspase-3 and caspase-7 in Cy/Cy compared to +/+ and Cy/+ kidneys. Caspase-8 and caspase-9 activity was more than 100% increased in Cy/Cy compared to Cy/+ and +/+ kidneys. On immunoblotting, there was an increase of the proform of both caspase-8 and caspase-9 in Cy/Cy kidneys. There was also an increase in cytochrome c release into the cytosol and an increase in caspase-2 protein and activity in Cy/Cy kidneys. On ribonuclease protection assay there was no difference in FasL mRNA between +/+, Cy/+, and Cy/Cy kidneys. Short-term treatment of Cy/Cy rats with the caspase inhibitor IDN-8050 resulted in inhibition of caspase-3 and caspase-7 activity in the kidney.

CONCLUSION

In Cy/Cy kidneys with ADPKD, there was an increase of the proform of caspase-9, an increase in cytochrome c release into the cytosol, and an increase in caspase-2 protein and activity demonstrating involvement of the intrinsic pathway. There was an increase in the proform of caspase-8 demonstrating involvement of the extrinsic pathway. No differences in FasL mRNA were seen suggesting that the extrinsic pathway is independent of the death receptor ligand, FasL.

Functional Role of Caspases in Heat-Induced Testicular Germ Cell Apoptosis1

In the present study, we determined whether a pan caspase inhibitor could prevent or attenuate heat-induced germ cell apoptosis. Groups of five adult (8 wk old) C57BL/6 mice pretreated with vehicle (DMSO) or Quinoline-Val-Asp (Ome)-CH2-O-Ph (Q-VD-OPH), a new generation broad-spectrum caspase inhibitor, were exposed once to local testicular heating (43 degrees C for 15 min) and killed 6 h later. The inhibitor (40 mg/kg body weight) or vehicle was administered intraperitoneally (i.p.) 1 h before local testicular heating. Germ cell apoptosis was detected by TUNEL assay and quantitated as number of apoptotic germ cells per 100 Sertoli cells at stages XI-XII. Compared with controls (16.8 +/- 3.1), mild testicular hyperthermia within 6 h resulted in a marked activation (277.3 +/- 21.6) of germ cell apoptosis, as previously reported by us. Q-VD-OPH at this dose markedly inhibited caspase 3 activation and significantly prevented (by 67.0%) heat-induced germ cell apoptosis. Q-VD-OPH-mediated rescue of germ cells was independent of cytosolic translocation of mitochondrial cytochrome c and DIABLO. Electron microscopy further revealed normal appearance of these rescued cells. Similar protection from heat-induced germ cell apoptosis was also noted after pretreatment with minocycline, a second-generation tetracycline that effectively inhibits cytochrome c release and, in turn, caspase activation. Collectively, the present study emphasizes the role of caspases in heat-induced germ cell apoptosis.

IL-18 Receptor Expression on Epithelial Cells is Upregulated by TNF Alpha

IL-18 is a multifunctional cytokine that augments both innate and acquired immunity and potentiates Th1 and Th2 reactions. We studied the expression of IL-18 receptor (IL-18R) on renal and respiratory epithelial cell lines. Both cell lines upregulated IL-18R mRNA and IL-18R membrane expression in response to TNF alpha and other proinflammatory cytokines. The function of IL-18R was confirmed by induction of IL-8 release from epithelial cells in response to recombinant IL-18. Epithelial cells may represent an important target for IL-18, mainly under inflammatory conditions associated with TNF alpha release.

Endotoxemic acute renal failure is attenuated in caspase-1-deficient mice

Caspase-1-deficient (-/-) mice are protected against sepsis-induced hypotension and mortality. We investigated the role of caspase-1 and its associated cytokines in a nonhypotensive model of endotoxemic acute renal failure (ARF). Mice were injected intraperitoneally with 2.5 mg of LPS that induces endotoxemic ARF. On immunoblot analysis of whole kidney, there was an increase in caspase-1 protein in LPS-treated mice compared with vehicle-treated controls. In LPS-treated mice, the glomerular filtration rate (GFR) was significantly higher in caspase-1 -/- vs. wild-type mice at 16 and 36 h after LPS. To determine the mechanism of this protection, the caspase-1-activated cytokines IL-1beta and IL-18 were investigated. IL-1beta and IL-18 protein were significantly increased in the kidneys of LPS- vs. vehicle-treated mice. To determine the role of these cytokines, mice were treated with recombinant IL-1 receptor antagonist (IL-1Ra) or IL-18-neutralizing antiserum. In LPS-treated mice, GFR was not different in IL-1Ra-treated or IL-18-neutralizing antiserum-treated or combination therapy (IL-1Ra plus IL-18-neutralizing antiserum-treated) compared with control mice. In addition, tubular cell apoptosis, neutrophil infiltration, myeloperoxidase activity, caspase-3 activity, and calpain activity were not different between wild-type and caspase-1 -/- mice with endotoxemic ARF. In LPS- vs. vehicle-treated wild-type mice, renal IL-1alpha was significantly increased. In both LPS- and vehicle-treated caspase-1 -/- mice, renal IL-1alpha was very low. In summary, caspase-1 -/- mice are functionally protected against endotoxemic ARF. Neutralization of IL-1beta and IL-18 is not functionally protective. The role of the intracellular proinflammatory cytokine IL-1alpha in endotoxemic ARF merits further study.

Regulation of caspase-3 and -9 activation in oxidant stress to RTE by forkhead transcription factors, Bcl-2 proteins, and MAP kinases

Cytotoxicity to renal tubular epithelial cells (RTE) is dependent on the relative response of cell survival and cell death signals triggered by the injury. Forkhead transcription factors, Bcl-2 family member Bad, and mitogen-activated protein kinases are regulated by phosphorylation that plays crucial roles in determining cell fate. We examined the role of phosphorylation of these proteins in regulation of H2O2-induced caspase activation in RTE. The phosphorylation of FKHR, FKHRL, and Bcl-2 family member Bad was markedly increased in response to oxidant injury, and this increase was associated with elevated levels of basal phosphorylation of Akt/protein kinase B. Phosphoinositol (PI) 3-kinase inhibitors abolished this phosphorylation and also decreased expression of antiapoptotic proteins Bcl-2 and BclxL. Inhibition of phosphorylation of forkhead proteins resulted in a marked increase in the proapoptotic protein Bim. These downstream effects of PI 3-kinase inhibition promoted the oxidant-induced activation of caspase-3 and -9, but not caspase-8 and -1. The impact of enhanced activation of caspases by PI 3-kinase inhibition was reflected on accelerated oxidant-induced cell death. Oxidant stress also induced marked phosphorylation of ERK1/2, P38, and JNK kinases. Inhibition of ERK1/2 phosphorylation but not P38 and JNK kinase increased caspase-3 and -9 activation; however, this activation was far less than induced by inhibition of Akt phosphorylation. Thus the Akt-mediated phosphorylation pathway, ERK signaling, and the antiapoptotic Bcl-2 proteins distinctly regulate caspase activation during oxidant injury to RTE. These studies suggest that enhancing renal-specific survival signals may lead to preservation of renal function during oxidant injury.

Impaired monocyte cytokine production in critically ill patients with acute renal failure

BACKGROUND

Plasma levels of pro- and anti-inflammatory cytokines are predictive of mortality in patients with acute renal failure (ARF). Anti-inflammatory strategies are postulated to be beneficial in treatment. However, there are few studies simultaneously examining monocyte cytokine production and plasma cytokine levels in patients with ARF.

METHODS

Study populations consisted of 20 critically ill patients with ARF, 19 critically ill patients without ARF (CRIT ILL), 28 healthy subjects (HS), 19 patients with chronic kidney disease (CKD), and 15 patients with end-stage renal disease (ESRD). Monocyte intracellular content of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8, and tumor necrosis factor-alpha (TNF-alpha) was determined by flow cytometry in whole blood. Plasma interleukin 6 and TNF-alpha concentrations were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

At baseline, there were no differences in intracellular monocyte cytokine levels between groups. After lipopolysaccaride stimulation, monocyte production of IL-1beta, TNF-alpha, and IL-6 in ARF patients was reduced by 41%, 84%, and 45%, respectively, compared to healthy subjects (P < 0.01 in each case), and similarly reduced compared to CKD and ESRD patients, and were similar to CRIT ILL patients. Plasma IL-6 levels were significantly higher in ARF patients than healthy subjects, CKD, and ESRD patients (all P < 0.001).

CONCLUSION

Critically ill patients with acute renal failure have impaired monocyte cytokine production and elevated plasma cytokine levels in a pattern that closely resembles critically ill patients without ARF, and that is dissimilar to CKD and ESRD patients.

Excess apoptosis of mononuclear cells contributes to the depressed cytomegalovirus-specific immunity in HIV-infected patients on HAART

HIV-infected patients on highly active antiretroviral therapy (HAART) have persistently decreased cytomegalovirus (CMV)-specific proliferative responses [lymphocyte proliferation assay (LPA)] in spite of increases in CD4+ T cell counts. Here we demonstrate an association between apoptosis of unstimulated peripheral blood mononuclear cells (uPBMC) and decreased CMV-LPA. HAART recipients had more apoptosis of uPBMC than controls when measured by caspases 3, 8, and 9 activities and by annexin V binding. Patients with undetectable HIV replication maintained significantly higher apoptosis of CD4+ and CD14+ cells compared to controls. CMV-LPA decreased with higher apoptosis of uPBMC in patients only. This association was independent of CD4+ cell counts or HIV replication. Furthermore, rescuing PBMC from apoptosis with crmA, but not with TRAIL- or Fas-pathway blocking agents or with other caspase inhibitors, increased CMV-LPA in HAART recipients. This effect was not observed in uninfected controls, further indicating that the down regulatory effect of apoptosis on cell-mediated immunity (CMI) was specifically associated with the HIV-infected status.

Caspase inhibition protects against reovirus-induced myocardial injury in vitro and in vivo

Viral myocarditis is a disease with a high morbidity and mortality. The pathogenesis of this disease remains poorly characterized, with components of both direct virus-mediated and secondary inflammatory and immune responses contributing to disease. Apoptosis has increasingly been viewed as an important mechanism of myocardial injury in noninfectious models of cardiac disease, including ischemia and failure. Using a reovirus murine model of viral myocarditis, we characterized and targeted apoptosis as a key mechanism of virus-associated myocardial injury in vitro and in vivo. We demonstrated caspase-3 activation, in conjunction with terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling and annexin binding, in cardiac myocytes after myocarditic viral infection in vitro. We also demonstrated a tight temporal and geographical correlation between caspase-3 activation, histologic injury, and viral load in cardiac tissue after myocarditic viral infection in vivo. Two pharmacologic agents that broadly inhibit caspase activity, Q-VD-OPH and Z-VAD(OMe)-FMK, effectively inhibited virus-induced cellular death in vitro. The inhibition of caspase activity in vivo by the use of pharmacologic agents as well as genetic manipulation reduced virus-induced myocardial injury by 40 to 60% and dramatically improved survival in infected caspase-3-deficient animals. This study indicates that apoptosis plays a critical role in mediating cardiac injury in the setting of viral myocarditis and is the first demonstration that caspase inhibition may serve as a novel therapeutic strategy for this devastating disease.

Urinary interleukin-18 is a marker of human acute tubular necrosis

BACKGROUND

Interleukin-18 (IL-18) is a mediator of ischemic acute tubular necrosis (ATN) in mice.

METHODS

IL-18 was measured in human urine to determine whether it might serve as a marker of ATN. Seventy-two patients, including healthy controls, patients with different forms of acute renal failure, and patients with other renal diseases, were studied.

RESULTS

Patients with ATN had significantly greater median urinary IL-18 concentrations than those with all other conditions: patients with ATN, 644 pg/mg creatinine (mean, 814 +/- 151 [SE] pg/mg creatinine; P <0.0001) versus healthy controls, 16 pg/mg creatinine (mean, 23 +/- 9 pg/mg creatinine); patients with prerenal azotemia, 63 pg/mg creatinine (mean, 155 +/- 68 pg/mg creatinine); patients with urinary tract infection, 63 pg/mg creatinine (mean, 149 +/- 110 pg/mg creatinine); those with chronic renal insufficiency, 12 pg/mg creatinine (mean, 84 +/- 45 pg/mg creatinine); and patients with nephrotic syndrome, 34 pg/mg creatinine (mean, 67 +/- 47 pg/mg creatinine). Median urinary IL-18 concentrations measured in the first 24 hours after kidney transplantation were 924 pg/mg creatinine (mean, 1,199 +/- 187 pg/mg creatinine) in patients who received a cadaveric kidney that developed delayed graft function compared with 171 pg/mg creatinine (mean, 367 +/- 102 pg/mg creatinine) in patients who received a cadaveric kidney with prompt graft function and 73 pg/mg creatinine (mean, 176 +/- 107 pg/mg creatinine) in patients who received a kidney with prompt graft function from a living donor (P <0.002). In kidney transplant recipients, lower urinary IL-18 levels were associated with a steeper decline in serum creatinine concentrations postoperative days 0 to 4 (P = 0.009).

CONCLUSION

IL-18 levels are elevated in urine in patients with ATN and delayed graft function compared with other renal diseases. Urinary IL-18 may serve as a marker for proximal tubular injury in ATN. The clinical application of this test may be substantial because it is reliable, inexpensive, and easy to perform.

Inhibition of apoptosis by Zn2+ in renal tubular cells following ATP depletion

Apoptosis has been implicated in ischemic renal injury. Thus one strategy of renal protection is to antagonize apoptosis. However, apoptosis inhibitory approaches remain to be fully explored. Zn(2+) has long been implicated in apoptosis inhibition; but systematic analysis of the inhibitory effects of Zn(2+) is lacking. Moreover, whether Zn(2+) blocks renal cell apoptosis following ischemia is unknown. Here, we demonstrate that Zn(2+) is a potent apoptosis inhibitor in an in vitro model of renal cell ischemia. ATP depletion induced apoptosis in cultured renal tubular cells, which was accompanied by caspase activation. Zn(2+) at 10 microM inhibited both apoptosis and caspase activation, whereas Co(2+) was without effect. In ATP-depleted cells, Zn(2+) partially prevented Bax activation and cytochrome c release from mitochondria. In isolated cell cytosol, Zn(2+) blocked cytochrome c-stimulated caspase activation at low-micromolar concentrations. In addition, Zn(2+) could directly antagonize the enzymatic activity of purified recombinant caspases. We conclude that Zn(2+) is a potent inhibitor of apoptosis in renal tubular cells following ATP depletion. Zn(2+) blocks apoptosis at multiple steps including Bax activation, cytochrome c release, apoptosome function, and caspase activation.

Role of caspases in renal tubular epithelial cell injury

The regulation of cell death has been investigated in a number of clinical disorders including renal ischemic and toxic acute renal failure. Caspases play a crucial role in the execution or final phase of cell death by cleaving and inactivating various structural and functional intracellular proteins that are essential for cell survival and proliferation. Evidence is now emerging to implicate the caspase pathway in a variety of renal diseases including the pathogenesis of acute renal failure. Among the 14 known members of the caspase family thus far identified several executioner caspases including caspases-3, -6, and -7 and the proinflammatory caspase including caspase-1 may participate in the final degradation of intracellular proteins. The activation of these caspases is regulated by the receptor- and mitochondrial-mediated cell signaling pathways as well as by the endoplasmic reticulum stress response. While the role of some caspases in renal injury is emerging, the roles of various proinflammatory and other executioner caspases remain to be determined. Although many pro- and anti-apoptotic molecules that act upstream of caspase activation have been identified, their regulation is yet to be determined in the pathogenesis of renal injury. A precise description of caspase-mediated cell death pathway and regulation of caspase activation is, therefore, critical to the understanding of the mechanism of renal injury and to the development of therapeutic targets that prevent renal diseases and preserve renal function.

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.

Antirestenotic Effects of a Locally Delivered Caspase Inhibitor in a Balloon Injury Model

BACKGROUND

The precise role of arterial barotrauma-mediated apoptosis in causing restenosis is unclear. The purpose of this study was to determine if a link exists between angioplasty-mediated medial smooth muscle cell apoptosis and subsequent neointimal hyperplasia.

METHODS AND RESULTS

Bilateral iliac artery angioplasty was performed in 25 male New Zealand White rabbits. Simultaneous with balloon injury, each artery was treated locally with either the caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(Ome)-fluoromethylketone (ZVAD-fmk) or control. In the acute cohort that was survived to 4 hours (n=10, 7 high dose and 3 low dose), an apoptotic index was calculated using the terminal deoxynucleotidyl TUNEL method. In the intermediate cohort that was survived to 2 weeks (n=5), luminal reendothelialization was measured via CD-31 staining. In the chronic cohort that was survived to 4 weeks (n=10), neointimal area was measured. In the acute cohort, there was a 40% reduction in the apoptotic index with high-dose ZVAD-fmk (P=0.008) and a 33% reduction with low-dose ZVAD-fmk (P=0.08). At 2 weeks, there was no significant difference in the degree of luminal reendothelialization. However, at 4 weeks, there was a 33% (0.33+/-0.23 versus 0.22+/-0.20 mm2) (P<0.005) reduction in neointimal area in ZVAD-fmk-treated arteries.

CONCLUSIONS

The local delivery of ZVAD-fmk during balloon injury inhibits smooth muscle cell apoptosis. This corresponds to a significant reduction in neointimal proliferation seen at 4 weeks without a significant change in the degree of reendothelialization at 2 weeks.

Gene expression in early ischemic renal injury: clues towards pathogenesis, biomarker discovery, and novel therapeutics

Acute renal failure (ARF) represents a common and serious problem in clinical medicine. Renal ischemia-reperfusion injury (IRI) is the major cause of ARF in the native and transplanted kidney. Several decades of research have provided successful therapeutic approaches in animal models, but translational efforts in humans have yielded disappointing results. The major reasons for this include a lack of early markers for ARF (and hence a delay in initiating therapy), and the multi-factorial nature of the disease. This review focuses on the use of cDNA microarrays to elucidate the molecular genetic mechanisms underlying tubule cell apoptosis, and to identify novel biomarkers for early renal IRI. Also presented is a comparative temporal analysis of cDNA microarray results from mature kidneys following IRI and during normal nephrogenesis. Molecular genetic evidence for the notion that regeneration recapitulates development in the kidney, and that injured tubule cells possess the capacity to de-differentiate to the earliest stages of development, is presented. The implications of these findings to the ability of the kidney to repair itself and potential strategies for accelerating recovery are briefly discussed.

Myeloperoxidase in kidney disease

In glomerular and tubulointerstitial disease, polymorphonuclear- and monocyte-derived reactive oxygen species may contribute to oxidative modification of proteins, lipids, and nucleic acids. In part, the processes instigated by reactive oxygen species parallel events that lead to the development of atherosclerosis. Myeloperoxidase (MPO), a heme protein and catalyst for (lipo)protein oxidation is present in these mononuclear cells. The ability of MPO to generate hypochlorous acid/hypochlorite (HOCl/OCl-) from hydrogen peroxide in the presence of chloride ions is a unique and defining activity for this enzyme. The MPO-hydrogen peroxide-chloride system leads to a variety of chlorinated protein and lipid adducts that in turn may cause dysfunction of cells in different compartments of the kidney. The aim of this article is to cover and interpret some experimental and clinical aspects in glomerular and tubulointerstitial diseases in which the MPO-hydrogen peroxide-chloride system has been considered an important pathophysiologic factor in the progression but also the attenuation of experimental renal disease. The colocalization of MPO and HOCl-modified proteins in glomerular peripheral basement membranes and podocytes in human membranous glomerulonephritis, the presence of HOCl-modified proteins in mononuclear cells of the interstitium and in damaged human tubular epithelia, the inflammation induced and exacerbated by MPO antibody complexes in necrotizing glomerulonephritis, and the presence of HOCl-modified epitopes in urine following hyperlipidemia-induced renal damage in rodents suggest that MPO is an important pathogenic factor in glomerular and tubulointerstitial diseases. Specifically, the interaction of MPO with nitric oxide metabolism adds to the complexity of actions of oxidants and may help to explain bimodal partly detrimental partly beneficial effects of the MPO-hydrogen peroxide-chloride system in redox-modulated renal diseases.

Acute renal failure after whole body ischemia is characterized by inflammation and T cell-mediated injury

Acute renal failure (ARF) commonly occurs after whole body ischemia. Most experimental models of ARF have relied on the isolated renal artery clamping model; however, there is a pressing need to develop and understand the pathogenesis of new models with more "clinical relevance." We evaluated a new murine model of ARF after whole body ischemia reperfusion injury (WBIRI). WBIRI was induced by an infusion of potassium chloride and a cardiac arrest period of 10 min. Resuscitation was achieved by cardiac compressions, ventilation, epinephrine, and fluids. WBIRI leads to a significant increase in serum creatinine (SCr) and renal tubular injury by 24 h. Renal myeloperoxidase (MPO) levels increased at 24 h after WBIRI. Increased expression of the proinflammatory genes, ICAM-1 and IL-6, was also observed in the kidney following WBIRI. On the basis of recent data that T cells are important mediators of isolated renal IRI, WBIRI was evaluated in T cell-deficient nu/nu mice. T cell-deficient mice had a significantly reduced rise in SCr and decreased tubular injury compared with wild-type mice. T cell-deficient mice had a decrease in ICAM-1 expression after WBIRI, but no decrease in renal MPO. This study describes a new, clinically relevant, model of ARF after WBIRI in mice and identifies the T cell as an important mediator of renal injury following WBIRI. Reduced ICAM-1 expression may provide a mechanism for this involvement.

Tubular apoptosis in the pathophysiology of renal disease

Apoptosis of renal tubular epithelial cells plays a major role in acute renal failure. Several external and internal signals can induce apoptosis, which is then effectuated via several pathways. These pathways are either the FAS/FAS-L pathway and downstream MAPK (mitogen-activated protein kinases) and JNK (c-Jun N-terminal kinase) signal transduction, or the RANK/RANK-L (receptor activator of NFkB) pathway via activation of the caspase cascade. Other pathways, especially for apoptosis induction by toxins, include the mitochondrial permeability transition pore activation and Bcl-2 superfamily member differential regulation. An important final, irreversible branch of these pathways is the release of cytochrome c from the mitochondria, leading to nuclear fragmentation. Therapeutic interventions of acute tubular injury focus on the prevention of apoptosis by either modulation of the balance of the bcl-2 family or by selectively blocking angiotensin receptors. It is not clear yet, which receptor blockade or combination of receptor blockers are most effective in apoptosis prevention. In chronic renal failure, tubular apoptosis has been found in biopsies from polycystic kidneys, but not in a quantitatively meaningful amount in other chronic human renal diseases. On the other hand, given the short half-life of apoptotic cells of few hours, even low numbers over time might turn out to be important modulators of chronic kidney disease, which are characterized by tubular cell loss. Potential therapeutic interventions to prevent tubular apoptosis in chronic renal disease include angiotensin system inhibition, whereby the angiotensin II AT2 receptor blockade seems more promising in apoptosis inhibition than the inhibition of other receptor subtypes.