Effect of Sirolimus on Native Total Kidney Volume After Transplantation in Patients with Autosomal Dominant Polycystic Kidney Disease: A Randomized Controlled Pilot Study.

BACKGROUND: The mammalian target of rapamycin (mTOR) pathway has been shown to be central to cyst formation and growth in patients with autosomal dominant polycystic kidney disease (ADPKD). Drugs that suppress mTOR signaling are frequently used as antiproliferative agents for maintenance immunosuppression in patients who have undergone kidney transplantation. The aim of this study was to determine the effect of sirolimus, an mTOR inhibitor, on cyst volume regression in patients with ADPKD who have undergone renal transplantation. METHODS: In this single-center, prospective, open-label, parallel-group, randomized trial, 23 adult patients with ADPKD who successfully underwent renal transplantation from 2008 to 2012 were subsequently randomized (on a 1:1 basis) to a maintenance immunosuppression regimen with either sirolimus (sirolimus, tacrolimus, prednisone) or mycophenolate (mycophenolate, tacrolimus, prednisone). Total kidney volumes were measured by means of high-resolution magnetic resonance imaging within 2 weeks after transplantation and at 1 year. The primary end point was change in total kidney volume at 1 year. RESULTS: Sixteen patients completed the 1-year study (8 patients in each group). There was a decrease in kidney volume in both the sirolimus group (percentage change from baseline, 20.5%; P < .001) and mycophenolate group (percentage change from baseline, 17%; P = .048), but there was no significant difference in percentage change of total kidney volume between the groups (P = .665). CONCLUSIONS: In ADPKD patients at 1 year after kidney transplantation, there was a similar decrease in polycystic kidney volume in patients receiving an immunosuppression regimen containing sirolimus compared with patients receiving mycophenolate.

Increased levels of soluble ST2 in patients with active newly diagnosed ANCA-associated vasculitis.

OBJECTIVE: ST2, a member of the interleukin-1 receptor family, is selectively expressed on Th2 cells and mediates important Th2 functions. IL-33 is a specific ligand of ST2. The aim of the study was to determine whether serum levels of soluble ST2 (sST2) or IL-33 predict activity of the disease in patients with ANCA-associated vasculitides (AAV). METHODS: 139 AAV patients and 62 controls were studied. IL-33 and sST2 in the blood were measured with a commercially available ELISA. RESULTS: Newly diagnosed AAV patients had higher sST2 levels than controls (P < 0.01). Levels of sST2 were significantly higher in active newly diagnosed AAV patients than in patients with remission (P < 0.001). IL-33 levels were higher in AAV patients than in the control groups (P = 0.002). However, serum IL-33 levels were not increased in patients with active AAV compared to patients in remission. IL-33 levels were higher in patients with granulomatosis with polyangiitis than in patients with microscopic polyangiitis (P = 0.012). CONCLUSIONS: Serum sST2, but not serum IL-33, may be a marker of activity in AAV patients.

Cytokines in acute kidney injury (AKI).

In acute kidney injury (AKI), many cytokines are released by leukocytes and renal tubular cells in the injured kidney and are important components of both the initiation and extension of inflammation. Cytokines are 1) produced by the kidney and mediate AKI, 2) produced by the kidney, released into the blood or urine and serve as biomarkers of AKI, and 3) produced by the kidney or other organs in AKI and mediate or protect against distant organ injury. Further understanding of the role of cytokines in AKI may result in therapeutic approaches like cytokine inhibition that may reduce the degree of kidney injury itself, as well as deleterious effects of kidney injury on other organs.

Therapeutic and predictive targets of AKI.

Acute kidney injury (AKI) is a very common condition encountered in a hospital setting. AKI is an independent risk factor for in-hospital mortality. In this review, we discuss in detail about the tubular, inflammatory and vascular molecular targets of AKI which may result in therapies to improve mortality and biomarkers for earlier diagnosis of AKI.

HIV-associated nephropathy in Caucasians: case report and review of literature.

HIV-associated nephropathy (HIVAN) is almost exclusively seen in African-Americans (AA) and is rare in Caucasians. The mechanisms responsible for the predilection of HIVAN in AA are not well understood. In transgenic mouse studies, genetic background plays a vital role in the development of the HIVAN phenotype. Larger studies in humans have been initiated to study genetic polymorphisms responsible for HIVAN. As our case illustrates, HIVAN should be considered in Caucasian patients with HIV infection complicated by nephrotic syndrome and renal failure.

VEGF receptor inhibition slows the progression of polycystic kidney disease.

Although the receptors for vascular endothelial growth factor (VEGF) exert their effects on vasculogenesis and angiogenesis through receptors located on endothelial cells, recent studies have shown that these receptors are also present on renal tubular epithelial cells. We investigated the role of VEGF on increased tubule cell proliferation in the Han:SPRD heterozygous (Cy/+) rat model of polycystic kidney disease. The levels of VEGF in the kidneys and the serum, and the expression of the two receptors on tubules were increased in Cy/+ rats. These rats were given ribozymes that specifically inhibited VEGFR1 and VEGFR2 mRNA expression. Tubule cell proliferation within the cysts was significantly decreased in the ribozyme-treated animals leading to decreased cystogenesis, blunted renal enlargement, and prevented the loss of renal function. Our studies show that inhibition of VEGF function may be an important therapeutic option to delay the progression of polycystic kidney disease.

Urine NGAL and IL-18 are predictive biomarkers for delayed graft function following kidney transplantation.

Delayed graft function (DGF) due to tubule cell injury frequently complicates deceased donor kidney transplants. We tested whether urinary neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) represent early biomarkers for DGF (defined as dialysis requirement within the first week after transplantation). Urine samples collected on day 0 from recipients of living donor kidneys (n = 23), deceased donor kidneys with prompt graft function (n = 20) and deceased donor kidneys with DGF (n = 10) were analyzed in a double blind fashion by ELISA for NGAL and IL-18. In patients with DGF, peak postoperative serum creatinine requiring dialysis typically occurred 2-4 days after transplant. Urine NGAL and IL-18 values were significantly different in the three groups on day 0, with maximally elevated levels noted in the DGF group (p < 0.0001). The receiver-operating characteristic curve for prediction of DGF based on urine NGAL or IL-18 at day 0 showed an area under the curve of 0.9 for both biomarkers. By multivariate analysis, both urine NGAL and IL-18 on day 0 predicted the trend in serum creatinine in the posttransplant period after adjusting for effects of age, gender, race, urine output and cold ischemia time (p < 0.01). Our results indicate that urine NGAL and IL-18 represent early, predictive biomarkers of DGF.

Urinary IL-18 is an early predictive biomarker of acute kidney injury after cardiac surgery.

Acute kidney injury (AKI) is a frequent complication of cardiopulmonary bypass (CPB). The lack of early biomarkers for AKI has impaired our ability to intervene in a timely manner. Urinary neutrophil gelatinase-associated lipocalin (NGAL) is recently demonstrated as an early biomarker of AKI after CPB, increasing 25-fold within 2 h and declining 6 h after surgery. In the present study, we tested whether interleukin-18 (IL-18) is a predictive biomarker for AKI in the same group of patients following CPB. Exclusion criteria included pre-existing renal insufficiency and nephrotoxin use. Serial urine samples were analyzed by enzyme-linked immunosorbent assay for IL-18 in 20 patients who developed AKI (defined as a 50% or greater increase in serum creatinine after CPB) and 35 controls (age, race, and gender-matched patients who did not develop AKI after CPB). Using serum creatinine, AKI was detected only 48-72 h after CPB. In contrast, urine IL-18 increased at 4-6 h after CPB, peaked at over 25-fold at 12 h, and remained markedly elevated up to 48 h after CPB. The performance of IL-18 as demonstrated by area under the receiver operating characteristics curve for diagnosis of AKI at 4, 12, and 24 h after CPB was 61, 75, and 73% respectively. Also, on multivariate analysis, both IL-18 and NGAL were independently associated with number of days in AKI among cases. Our results indicate that IL-18 is an early, predictive biomarker of AKI after CPB, and that NGAL and IL-18 are increased in tandem after CPB. The combination of these two biomarkers may allow for the reliable early diagnosis and prognosis of AKI at all times after CPB, much before the rise in serum creatinine.

Caspases as drug targets in ischemic organ injury.

Caspases are intracellular cysteine proteases that mediate cell death and inflammation. Caspase-3 is a major mediator of both apoptotic and necrotic cell death. Caspase-1 mediates inflammation though the activation of the cytokines interleukin-1beta (IL-1beta) and interleukin-18 (IL-18). Increases in both caspase-1 and -3 have been described in ischemic injury to various organs including brain, heart and kidney. Both pharmacological inhibitors and genetic approaches have been used to inhibit caspases in vivo. Pancaspase inhibitors protect against ischemic injury in brain, heart and kidney. Pancaspase inhibition also reduces cold preservation injury due to apoptosis in liver endothelial cells and prolongs animal survival after orthotopic liver transplantation. Caspase-1 inhibition or caspase-1 deficiency protects against ischemic injury in brain, heart and kidney models of ischemia. Specifically, impaired IL-18 processing protects caspase-1-deficient mice from ischemic acute renal failure. This review focuses on studies of caspase-1 and pancaspase inhibition in ischemic injury to brain, heart and kidney. In addition, the studies of pancaspase inhibition in cold ischemic injury and organ preservation will be reviewed. The therapeutic potential of caspase inhibition in ischemic injury will be discussed.

Diuretics versus angiotensin-converting enzyme inhibitors in autosomal dominant polycystic kidney disease.

Hypertension, which occurs commonly and early in autosomal dominant polycystic kidney disease (ADPKD), affects both renal and patient outcome. However, there is no consensus about the type of antihypertensive therapy that is most appropriate for patients with ADPKD. This historical prospective, nonrandomized study was designed to investigate the effect on renal function of diuretics versus angiotensin-converting enzyme (ACE) inhibitors in hypertensive patients with ADPKD who entered the study with comparable renal function. Among hypertensive ADPKD patients followed in our center, patients taking diuretics without any ACE inhibitors were included in the diuretic group (n = 14, male/female ratio 5/9, mean age 47 years), whereas patients taking ACE inhibitors but no diuretics were included in the ACE inhibitor (ACEI) group (n = 19, male/female ratio 11/8, mean age 41 years). For comparable blood pressure control, 21% of the ACEI group and 64% of the diuretic group (p < 0.05) needed additional antihypertensive medications. After an average follow-up period of 5.2 years, the creatinine clearance decreased significantly in the diuretic group (74 vs. 46 ml/min/1.73 m2, p < 0.0001) and in the ACEI group (83 vs. 71 ml/min/1.73 m2, p = 0.0005). The decrement in creatinine clearance was significantly larger in the diuretic group than the ACEI group (p < 0.05). The annual decrease in creatinine clearance was 5.3 ml/min/1.73 m2 in the diuretic group and 2.7 ml/min/1.73 m2 in the ACEI group (p < 0.05). A significant increase in urinary protein excretion occurred in the diuretic but not in the ACEI group. Hypertensive ADPKD patients treated with diuretics had a faster loss of renal function as compared with patients treated with ACE inhibitors, despite similar blood pressure control. This result will need to be further examined in a randomized study.

Impaired IL-18 processing protects caspase-1-deficient mice from ischemic acute renal failure.

We sought to determine whether mice deficient in the proinflammatory caspase-1, which cleaves precursors of IL-1 beta and IL-18, were protected against ischemic acute renal failure (ARF). Caspase-1(-/-) mice developed less ischemic ARF as judged by renal function and renal histology. These animals had significantly reduced blood urea nitrogen and serum creatinine levels and a lower morphological tubular necrosis score than did wild-type mice with ischemic ARF. Since caspase-1 activates IL-18, lack of mature IL-18 might protect these caspase-1(-/-) mice from ARF. In wild-type animals, we found that ARF causes kidney IL-18 levels to more than double and induces the conversion of the IL-18 precursor to the mature form. This conversion is not observed in caspase-1(-/-) ARF mice or sham-operated controls. We then injected wild-type mice with IL-18-neutralizing antiserum before the ischemic insult and found a similar degree of protection from ARF as seen in caspase-1(-/-) mice. In addition, we observed a fivefold increase in myeloperoxidase activity in control mice with ARF, but no such increase in caspase-1(-/-) or IL-18 antiserum-treated mice. Finally, we confirmed histologically that caspase-1(-/-) mice show decreased neutrophil infiltration, indicating that the deleterious role of IL-18 in ischemic ARF may be due to increased neutrophil infiltration.

Endotoxemic renal failure in mice: Role of tumor necrosis factor independent of inducible nitric oxide synthase.

BACKGROUND: Renal failure is a frequent complication of sepsis with a high mortality. Tumor necrosis factor (TNF) has been suggested to be a factor in the acute renal failure in sepsis or endotoxemia. Recent studies also suggest involvement of nitric oxide (NO), generated by inducible NO synthase (iNOS), in the pathogenesis of endotoxin-induced renal failure. The present study tested the hypothesis that the role of TNF in endotoxic renal failure is mediated by iNOS-derived NO. METHODS: Renal function was evaluated in endotoxemic [Escherichia coli lipopolysaccharide (LPS), 5 mg/kg IP] wild-type and iNOS knockout mice. The effect of TNF neutralization on renal function during endotoxemia in mice was assessed by a TNF-soluble receptor (TNFsRp55). RESULTS: An injection of LPS to wild-type mice resulted in a 70% decrease in glomerular filtration rate (GFR) and in a 40% reduction in renal plasma flow (RPF) 16 hours after the injection. The results occurred independent of hypotension, morphological changes, apoptosis, and leukocyte accumulation. In mice pretreated with TNFsRp55, only a 30% decrease in GFR without a significant change in RPF in response to LPS, as compared with vehicle-treated mice, was observed. Also, the serum NO concentration was significantly lower in endotoxemic wild-type mice pretreated with TNFsRp55, as compared with untreated endotoxemic wild-type mice (260 +/- 52 vs. 673 +/- 112 micromol/L, P < 0.01). In LPS-injected iNOS knockout mice and wild-type mice treated with a selective iNOS inhibitor, 1400W, the development of renal failure was similar to that in wild-type mice. As in wild-type mice, TNFsRp55 significantly attenuated the decrease in GFR (a 33% decline, as compared with 75% without TNFsRp55) without a significant change in RPF in iNOS knockout mice given LPS. CONCLUSIONS: These results demonstrate a role of TNF in the early renal dysfunction (16 h) in a septic mouse model independent of iNOS, hypotension, apoptosis, leukocyte accumulation, and morphological alterations, thus suggesting renal hypoperfusion secondary to an imbalance between, as yet to be defined, renal vasoconstrictors and vasodilators.

Role of polymeric Tamm-Horsfall protein in cast formation: oligosaccharide and tubular fluid ions.

BACKGROUND: In acute tubular necrosis (ATN), distal tubules are obstructed by casts formed by tubular debris, cells, and Tamm-Horsfall protein (THP). Since there are Arginine-Glycine-Aspartate (RGD) and Leucine-Aspartate-Valine (LDV) adhesive sequences in human THP, there may be direct integrin-mediated binding of tubular cells to THP. Alternatively, polymerization of THP may result in entrapment of the cells in its gel. METHODS: Adhesion of LLC-PK(1) cells to THP-coated wells was directly measured. THP concentrate was dissolved in solutions which mimic urine from ATN (ATN-S), distal convoluted tubule (DCT-S), collecting duct (CD-S), and monomeric buffer (M buffer). THP was also denatured by either boiling or N-glycanase digestion. Gel formation of THP was then measured. Inhibition of LLC-PK(1) cell adhesion to collagen type I was measured with each solution, as well as after the collagen was pretreated with either monomeric (mTHP) or polymeric (pTHP) THP. The effect of pTHP on the settling rate of LLC-PK(1) cells in suspension was also measured. RESULTS: LLC-PK(1) cells did not directly adhere to THP, a finding against integrin-mediated binding as a mechanism for in vivo tubular cell/THP cast formation. The high electrolyte concentration of ATN-S and CD-S, however, was associated with pTHP gel formation. Moreover, cells suspended in pTHP remained in suspension. In cell adhesion studies, mTHP attenuated cell adhesion by binding to the matrix, whereas pTHP attenuated cell adhesion by trapping cells in its gel. An active process was involved since both pTHP gel formation and attenuation of cell adhesion were abolished by boiling or oligosaccharide removal with N-glycanase digestion. CONCLUSIONS: With renal ischemia and proximal tubule cell shedding, ATN and collecting duct fluid composition enhance THP gel formation and thus favor tubular cast formation and obstruction. The present in vitro results indicate the importance of oligosaccharide residues in mediating the effect of the THP on gel formation and potential cast formation in ATN.

Calpain inhibition protects against virus-induced apoptotic myocardial injury.

Viral myocarditis is an important cause of human morbidity and mortality for which reliable and effective therapy is lacking. Using reovirus strain 8B infection of neonatal mice, a well-characterized experimental model of direct virus-induced myocarditis, we now demonstrate that myocardial injury results from apoptosis. Proteases play a critical role as effectors of apoptosis. The activity of the cysteine protease calpain increases in reovirus-infected myocardiocytes and can be inhibited by the dipeptide alpha-ketoamide calpain inhibitor Z-Leu-aminobutyric acid-CONH(CH(2))3-morpholine (CX295). Treatment of reovirus-infected neonatal mice with CX295 protects them against reovirus myocarditis as documented by (i) a dramatic reduction in histopathologic evidence of myocardial injury, (ii) complete inhibition of apoptotic myocardial cell death as identified by terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling, (iii) a reduction in serum creatine phosphokinase, and (iv) improved weight gain. These findings are the first evidence for the importance of a calpain-associated pathway of apoptotic cell death in viral disease. Inhibition of apoptotic signaling pathways may be an effective strategy for the treatment of viral disease in general and viral myocarditis in particular.

Downregulation of the calpain inhibitor protein calpastatin by caspases during renal ischemia-reperfusion.

The interaction between the cysteine proteases calpain and caspases during renal ischemia-reperfusion (I/R) was investigated. An increase in the activity of calpain, as determined by 1) the appearance of calpain-mediated spectrin breakdown products and 2) the conversion of procalpain to active calpain, was demonstrated. Because intracellular calpain activity is regulated by calpastatin, the effect of I/R on calpastatin was determined. On immunoblot of renal cortex, there was a 50-100% decrease of a low molecular weight (LMW) form of calpastatin (41 kDa) after I/R. Calpastatin activity was also significantly decreased after I/R compared with sham-operated rats, indicating that the decreased protein expression had functional significance. In rats treated with the caspase inhibitor, z-Asp-2,6-dichlorobenzoyloxymethylketone (Z-D-DCB), the decrease in both calpastatin activity and protein expression was normalized, suggesting that caspases may be proteolyzing calpastatin. Caspase 3 activity increased significantly after I/R and was attenuated in ischemic kidneys from rats treated with the caspase inhibitor. In summary, during renal I/R injury, there is 1) calpain activation associated with downregulation of calpastatin protein and decreased calpastatin activity and 2) activation of caspase 3. In addition, in vivo caspase inhibition reverses the decrease in calpastatin activity. In conclusion, proteolysis of calpastatin by caspase 3 may regulate calpain activity during I/R injury. Although the protective effect of cysteine protease inhibition against hypoxic necrosis of proximal tubules has previously been demonstrated, the functional significance in ischemic acute renal failure in vivo merits further study.

Progress in blood pressure control in autosomal dominant polycystic kidney disease.

Hypertension occurs commonly in autosomal dominant polycystic kidney disease (ADPKD) and is an important factor in the progression of the disease and cardiovascular mortality. The aim of this prospective 15-year study is to report the rate of blood pressure control and the potential effect of a 10-point education program developed by our center for ADPKD patients and their physicians. The patients' blood pressure treatment was managed by their primary care physicians. Three 5-year periods were analyzed in which similar rates of hypertension in patients with ADPKD were present (63% to 68%). In the first period (1985 to 1989), the rate of blood pressure control (<140/90 mm Hg) was 38% for 216 hypertensive patients with ADPKD. From 1990 to 1994, the percentage of blood pressure control increased to 55% in 194 hypertensive patients with ADPKD (P < 0.001 versus 1985 to 1989); and the level of blood pressure control increased to 64% in 181 hypertensive patients with ADPKD during 1995 to 1999 (P < 0.001 versus 1985 to 1989). Although this percentage of blood pressure control in patients with ADPKD remains suboptimal, it compares very favorably with the 27% estimated blood pressure control in patients with essential hypertension from 1991 to 1994 in the United States.

Effect of antihypertensive therapy on renal function and urinary albumin excretion in hypertensive patients with autosomal dominant polycystic kidney disease.

Hypertensive patients with autosomal dominant polycystic kidney disease (ADPKD) have a faster progression to end-stage renal disease (ESRD) than their normotensive counterparts. The aim of this prospective, randomized study is to compare the effects of the calcium channel blocker amlodipine and the angiotensin-converting enzyme inhibitor enalapril as first-line therapy on blood pressure, renal function, and urinary albumin excretion in hypertensive patients with ADPKD. Twenty-four patients with ADPKD with hypertension with creatinine clearances (Ccrs) greater than 50 mL/min/1.73 m(2) were included in the study. Twelve patients received amlodipine (mean dose, 9 mg/d), and 12 patients received enalapril (mean dose, 17 mg/d). The patients were followed up for 5 years. Baseline mean arterial pressures, which were 109 +/- 3 mm Hg in the amlodipine group and 108 +/- 3 mm Hg in the enalapril group, decreased significantly after 1 year of follow-up (amlodipine, 96 +/- 3 mm Hg; P < 0.005; enalapril, 89 +/- 2 mm Hg; P < 0.0005) and remained stable at year 5 (amlodipine, 97 +/- 3 mm Hg; P < 0.0005 versus baseline; enalapril, 94 +/- 3 mm Hg; P < 0.005 versus baseline). Ccrs, which were 83 +/- 5 mL/min/1.73 m(2) in the amlodipine group and 77 +/- 6 mL/min/1.73 m(2) in the enalapril group, remained stable after 1 year of follow-up and decreased significantly at year 3 in both groups (amlodipine, 67 +/- 5 mL/min/1.73 m(2); P < 0.01 versus year 1 and baseline; enalapril, 58 +/- 4 mL/min/1.73 m(2); P < 0.05 versus year 1 and P < 0.0005 versus baseline) with no significant change thereafter. No change was observed in urinary albumin-creatinine ratio in the amlodipine group (baseline, 68 +/- 21 mg/g; year 1, 52 +/- 21 mg/g; year 5, 148 +/- 74 mg/g), whereas it decreased significantly in the enalapril group at year 1 (baseline, 23 +/- 4 mg/g; year 1, 13 +/- 3 mg/g; P < 0.05) and remained stable until the end of the study at year 5 (14 +/- 6 mg/g). The investigators concluded that blood pressure was similar in both groups but only enalapril had a significant effect to sustain decreased urinary albumin excretion for a 5-year follow-up. Although proteinuria has been considered a surrogate of renal disease progression, further studies will be necessary to confirm this hypothesis in ADPKD, because after 5 years, no differences in renal function were observed between the enalapril and amlodipine groups. In comparison with patients with ADPKD with uncontrolled hypertension, effective control of blood pressure, as undertaken in the present study, should delay the onset of ESRD by approximately 15 years.