Blockade of angiotensin II with losartan attenuates transforming growth factor-beta1 inducible gene-h3 (betaig-h3) expression in a model of chronic cyclosporine nephrotoxicity

Model-Informed Vancomycin Dosing Optimization to Address Delayed Renal Maturation in Infants and Young Children with Critical Congenital Heart Disease

Ensuring safe and effective drug therapy in infants and young children often requires accounting for growth and organ development; however, data on organ function maturation are scarce for special populations, such as infants with congenital diseases. Children with critical congenital heart disease (CCHD) often require multiple staged surgeries depending on their age and disease severity. Vancomycin (VCM) is used to treat postoperative infections; however, the standard pediatric dose (60-80 mg/kg/day) frequently results in overexposure in children with CCHD. In this study, we characterized the maturation of VCM clearance in pediatric patients with CCHD and determined the appropriate dosing regimen using population pharmacokinetic (PK) modeling and simulations. We analyzed 1,254 VCM serum concentrations from 152 postoperative patients (3 days-13 years old) for population PK analysis. The PK model was developed using a two-compartment model with allometrically scaled body weight, estimated glomerular filtration rate (eGFR), and postmenstrual age as covariates. The observed clearance in patients aged ≤ 1 year and 1-2 years was 33% and 40% lower compared with that of non-CCHD patients, respectively, indicating delayed renal maturation in patients with CCHD. Simulation analyses suggested VCM doses of 25 mg/kg/day (age ≤ 3 months, eGFR 40 mL/min/1.73 m2 ) and 35 mg/kg/day (3 months < age ≤ 3 years, eGFR 60 mL/min/1.73 m2 ). In conclusion, this study revealed delayed renal maturation in children with CCHD, could be due to cyanosis and low cardiac output. Model-informed simulations identified the lower VCM doses for children with CCHD compared with standard pediatric guidelines.

Role of (Pro)Renin Receptor in Cyclosporin A-Induced Nephropathy

Calcineurin inhibitors (CNIs) such as cyclosporin A (CsA) have been widely used to improve graft survival following solid-organ transplantation. However, the clinical use of CsA is often limited by its nephrotoxicity. The present study tested the hypothesis that activation of (pro)renin receptor (PRR) contributes to CsA-induced nephropathy by activating the renin-angiotensin system (RAS). Renal injury in male Sprague-Dawley rats was induced by a low-salt diet combined with CsA as evidenced by elevated plasma creatinine and BUN levels, decreased creatinine clearance and induced renal inflammation, apoptosis as well as interstitial fibrosis, elevated urinary N-acetyl-β-D-glucosaminidase activity and urinary kidney injury molecular 1 content. Each index of renal injury was attenuated following a 2-wk treatment with a PRR decoy inhibitor PRO20. While CsA rats with kidney injury displayed increased renal sPRR abundance, plasma sPRR, renin activity, Ang II, and heightened urinary total prorenin/renin content; RAS activation was attenuated by PRO20. Exposure of cultured human renal proximal tubular HK-2 cells to CsA induced expression of fibronectin and sPRR production, but the fibrotic response was attenuated by PRO20 and siRNA-mediated PRR knockdown. These findings support the hypothesis that activation of PRR contributes to CsA-induced nephropathy by activating the RAS in rats. Of importance, we provide strong proof of concept that targeting PRR offers a novel therapeutic strategy to limit nephotoxic effects of immunosuppressant drugs.

Role of Klotho in Chronic Calcineurin Inhibitor Nephropathy

Calcineurin inhibitors (CNIs) are the most popular immunosuppressants in organ transplantation, but nephrotoxicity is a major concern. The common mechanism underlying chronic CNI nephropathy is oxidative stress, and the process of chronic CNI nephropathy is similar to that of aging. Current studies provide evidence that antiaging Klotho protein plays an important role in protecting against oxidative stress, and its signaling is a target for preventing oxidative stress-induced aging process. In this review, we focus on the association between Klotho and oxidative stress and the protective mechanism of action of Klotho against oxidative stress in chronic CNI nephropathy. In addition, we discuss the delivery strategy for Klotho in CNI-induced nephropathy.

Losartan and Dexamethasone may inhibit chemotaxis to reduce the infiltration of Th22 cells in IgA nephropathy

Angiotensin II is considered a major profibrotic factor that is involved in tissue remodeling processes, as the inhibition of Angiotensin II can halt renal inflammatory processes. Dexamethasone, an important anti-inflammatory and immunosuppressive agent, has been widely used to treat renal disease for decades. In this study, we explored the frequency of Th22 cells in a mouse model of IgA nephropathy and compared the possible effects of Losartan and Dexamethasone on Th22 cells. The experiments were performed using 6-week-old BALB/c female mice in an established IgA nephropathy model. The mice were randomly separated into 4 groups, which were administered Losartan (30mg/kg/d) or Dexamethasone (10mg/kg/d) and subjected to IgA nephropathy or the normal control treatment for 1month. The frequency of Th22 cells was measured via flow cytometry, and the relative pathological changes in renal morphology were measured with different pathological staining methods. Immunohistochemistry was performed to verify the expression of CCR10 and CCL27, which is specialized receptor on Th22 cells and its corresponding chemokine, respectively. The concentrations of CCL27 and IL-22 in renal tissue homogenates and sera were detected using ELISAs. Losartan and Dexamethasone differentially decreased the frequency of Th22 cells after 1month, and mesangial cell proliferation was also improved. Moreover, the expression of CCR10, CCL27 and IL-22 was reduced by treatment with either drug. However, significant differences between Losartan and Dexamethasone were not observed. Based on these findings, Losartan and Dexamethasone may suppress inflammatory responses by inhibiting the chemotaxis of Th22 cells in IgA nephropathy.

Expression of erythropoietin and its receptor in kidneys from normal and cyclosporine-treated rats

Long-term treatment with cyclosporine A (CsA) is associated with various types of complications; however, CsA-induced anemia has not been reported. The present study examined the impact of CsA on hematopoietic parameters and intrarenal expression of erythropoietin (EPO) and the EPO receptor (EPOR) in a rat model of chronic CsA nephrotoxicity. Sprague-Dawley rats were fed a low-salt diet (0.05% sodium) and were treated daily for 4 weeks with vehicle (olive oil 1 mL/kg subcutaneously) or CsA (15 mg/kg subcutaneously). The expression of EPO and EPOR was evaluated by immunohistochemistry and immunoblotting, and hematopoietic parameters were assessed by measuring blood hemoglobin and hematocrit levels, and these variables were compared between treatment groups. Renal function, oxidative stress, histopathology (tubulointerstitial fibrosis), apoptotic cell death, and expression of transforming growth factor β-inducible gene-h3 (βig-h3) were also compared between treatment groups. In kidneys from vehicle-treated rats, endogenous EPO and EPOR protein were expressed constitutively in the outer stripe of the outer medulla and the cortex. EPO protein expression decreased significantly in kidneys from CsA-treated rats. By contrast, EPOR expression was higher in kidneys from CsA-treated rats than in vehicle-treated rats. These changes were accompanied by decreases in serum hemoglobin and hematocrit levels and correlated with the number of cells positive for terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (r = -0.769, P = .003) and βig-h3 protein expression (r = -0.910, P < .001). Long-term treatment with CsA suppresses renal endogenous EPO expression, resulting in anemia. Increases in apoptotic cell death and βig-h3 expression are closely associated with inhibition of EPO expression in chronic CsA nephrotoxicity.

Clinical and hemodynamic effects of renin-angiotensin system blockade in cardiac transplant recipients

Chronic kidney disease continues to be a major limiting factor for long-term survival of heart transplant recipients. Little is known about the early use of renin-angiotensin system (RAS) blocking agents and their impact on renal function and hemodynamics in heart transplant recipients. In this cohort study all eligible recipients of orthotopic heart transplants at the UTAH cardiac transplantation program from 2001 through 2007 were divided into 2 groups-patients who were started on angiotensin-converting enzyme inhibitors or angiotensin receptor blockers within the first 4 weeks of transplantation and continued on these for ≥4 weeks during the first 3 months (RAS blockade group, n = 75) and those who were not (non-RAS blockade group, n = 52). All patients were followed for 1 year after transplantation. There were no significant differences at baseline between the 2 groups. Estimated glomerular filtration rate at 12 months was significantly higher in the RAS blockade group compared to the non-RAS blockade group (mean ± SD, 56.3 ± 22.4 vs 47.3 ± 18.1 ml/min/1.73 m(2), p = 0.036). At 12 months pulmonary artery systolic pressure was significantly lower in the RAS blockade group compared to the non-RAS blockade group (30.2 ± 7.4 vs 32.9 ± 9.3 mm Hg, p = 0.023). Left ventricular ejection fraction and pulmonary capillary wedge pressure were similar between the 2 groups. In conclusion, early RAS blockade after heart transplantation is safe, well tolerated, and associated with better renal function and hemodynamic profile at 1 year after transplantation.

Genomic-derived markers for early detection of calcineurin inhibitor immunosuppressant-mediated nephrotoxicity

Calcineurin inhibitor (CI) therapy has been associated with chronic nephrotoxicity, which limits its long-term utility for suppression of allograft rejection. In order to understand the mechanisms of the toxicity, we analyzed gene expression changes that underlie the development of CI immunosuppressant-mediated nephrotoxicity in male Sprague-Dawley rats dosed daily with cyclosporine (CsA; 2.5 or 25 mg/kg/day), FK506 (0.6 or 6 mg/kg/day), or rapamycin (1 or 10 mg/kg/day) for 1, 7, 14, or 28 days. A significant increase in blood urea nitrogen was observed in animals treated with CsA (high) or FK506 (high) for 14 and 28 days. Histopathological examination revealed tubular basophilia and mineralization in animals given CsA (high) or FK506 (low and high). We identified a group of genes whose expression in rat kidney is correlated with CI-induced kidney injury. Among these genes are two genes, Slc12a3 and kidney-specific Wnk1 (KS-Wnk1), that are known to be involved in sodium transport in the distal nephrons and could potentially be involved in the mechanism of CI-induced nephrotoxicity. The downregulation of NCC (the Na-Cl cotransporter coded by Slc12a3) in rat kidney following CI treatment was confirmed by immunohistochemical staining, and the downregulation of KS-Wnk1 was confirmed by quantitative real-time-polymerase chain reaction (qRT-PCR). We hypothesize that decreased expression of Slc12a3 and KS-Wnk1 could alter the sodium chloride reabsorption in the distal tubules and contribute to the prolonged activation of the renin-angiotensin system, a demonstrated contributor to the development of CI-induced nephrotoxicity in both animal models and clinical settings. Therefore, if validated as biomarkers in humans, SLC12A3 and KS-WNK1 could potentially be useful in the early detection and reduction of CI-related nephrotoxicity in immunosuppressed transplant patients when monitoring the health of kidney xenographs in clinical practice.

Angiotensin II blockade upregulates the expression of Klotho, the anti-ageing gene, in an experimental model of chronic cyclosporine nephropathy

BACKGROUND

The Klotho gene plays a role in suppressing ageing-related disorders. It is suggested that activation of renin-angiotensin system (RAS) or oxidative stress suppresses Klotho in the kidney. This study evaluated the association between Klotho expression and RAS in cyclosporine (CsA)-induced renal injury.

METHODS

Chronic CsA nephropathy was induced by administering CsA (30 mg/kg) to mice on a low-salt diet (LSD) for 4 weeks. A normal-salt diet (NSD) was used as the control. Reverse transcription-polymerase chain reaction, western blot and immunohistochemistry were performed for Klotho and intrarenal RAS activity was measured using immunohistochemistry for angiotensinogen and renin. Oxidative stress was measured with urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG).

RESULTS

CsA treatment decreased Klotho mRNA and protein in mouse kidney in a dose-dependent and time-dependent manner, but a concurrent treatment with losartan, an angiotensin II type 1 (AT1) receptor blocker, reversed the decrease in Klotho expression with histological improvement. This finding was more marked in the LSD than the NSD. Klotho expression was correlated with angiotensinogen and renin expression, tubulointerstitial fibrosis score and urinary 8-OHdG excretion.

CONCLUSIONS

Angiotensin II may play a pivotal role in regulating Klotho expression in CsA-induced renal injury. AT1 receptor blocker may inhibit the ageing process by decreasing oxidative stress caused by CsA.

The pathogenesis and treatment of chronic allograft nephropathy

Despite improvements in immunosuppressive therapy, long-term allograft survival after kidney transplantation remains as low as 50%. Chronic allograft nephropathy (CAN) is a major cause of late graft loss in renal transplant recipients. The histopathologic signs of CAN-interstitial fibrosis, tubular atrophy, glomerulopathy and vasculopathy-are nonspecific; therefore, the 2007 Banff classification dispensed with the term CAN in favor of 'interstitial fibrosis and tubular atrophy without evidence of any specific etiology'. In this Review, however, the term CAN is used to describe a clinical syndrome that is characterized by progressive decline in renal function from 3 months after transplantation, accompanied by the development of proteinuria and hypertension. The pathogenesis of CAN is complex and incompletely understood, and involves several immunological and non-immunological factors. We discuss the contributory roles of acute rejection, donor age, anti-human-leukocyte-antigen antibodies, calcineurin inhibitor nephrotoxic effects, viral infection, hypertension and hyperlipidemia. The prevention and treatment of CAN needs multidisciplinary strategies. Early detection by means of protocol biopsy and calculation of glomerular filtration rate is the first step, followed by management of modifiable risk factors.

Calcineurin inhibitor nephrotoxicity

The use of the calcineurin inhibitors cyclosporine and tacrolimus led to major advances in the field of transplantation, with excellent short-term outcome. However, the chronic nephrotoxicity of these drugs is the Achilles' heel of current immunosuppressive regimens. In this review, the authors summarize the clinical features and histologic appearance of both acute and chronic calcineurin inhibitor nephrotoxicity in renal and nonrenal transplantation, together with the pitfalls in its diagnosis. The authors also review the available literature on the physiologic and molecular mechanisms underlying acute and chronic calcineurin inhibitor nephrotoxicity, and demonstrate that its development is related to both reversible alterations and irreversible damage to all compartments of the kidneys, including glomeruli, arterioles, and tubulo-interstitium. The main question--whether nephrotoxicity is secondary to the actions of cyclosporine and tacrolimus on the calcineurin-NFAT pathway--remains largely unanswered. The authors critically review the current evidence relating systemic blood levels of cyclosporine and tacrolimus to calcineurin inhibitor nephrotoxicity, and summarize the data suggesting that local exposure to cyclosporine or tacrolimus could be more important than systemic exposure. Finally, other local susceptibility factors for calcineurin inhibitor nephrotoxicity are reviewed, including variability in P-glycoprotein and CYP3A4/5 expression or activity, older kidney age, salt depletion, the use of nonsteroidal anti-inflammatory drugs, and genetic polymorphisms in genes like TGF-beta and ACE. Better insight into the mechanisms underlying calcineurin inhibitor nephrotoxicity might pave the way toward more targeted therapy or prevention of calcineurin inhibitor nephrotoxicity.

Influence of angiotensin II on expression of toll-like receptor 2 and maturation of dendritic cells in chronic cyclosporine nephropathy

BACKGROUND

Angiotensin (Ang) II plays an important role in immune regulation. We evaluate the influence of the renin-angiotensin system (RAS) in the innate immune response caused by cyclosporine A (CsA)-induced renal injury.

METHODS

Two separate studies were performed in Sprague Dawley rats. First, losartan (LSRT, 10 mg/kg per day) was concurrently administered with CsA (15 mg/kg per day) for 28 days. Second, AngII (435 ng/kg/min) was infused with or without LSRT for 14 days.

RESULTS

AngII blockade with LSRT decreased toll-like receptor (TLR) 2 mRNA and protein expression, expression of tumor necrosis factor (TNF)-alpha mRNA, and expression of major histocompatibility complex class II antigen, which was upregulated in CsA-induced renal injury. The increased number of matured dendritic cells (DCs) in CsA-induced renal injury was also decreased by concomitant treatment of LSRT. Direct infusion of AngII increased TNF-alpha mRNA, TLR2 mRNA, and protein and the number of DCs, compared with the control rat kidney. In contrast, concomitant treatment of LSRT decreased all parameters.

CONCLUSION

AngII plays a pivotal role in activating the innate immune response in CsA-induced renal injury.

The challenge of renal function in heart transplant children

Renal dysfunction may occur after pediatric heart transplantation and impacts on long-term prognosis. This study aims to review the incidence and mechanisms of chronic nephropathy following heart transplantation, and suggest therapeutic directions. The proportion of pediatric heart-transplant recipients with impaired renal function varies from 22 to 57%, and end-stage renal failure from 3 to 10%, depending on the method used for estimating the glomerular filtration rate. The pathophysiology of renal dysfunction is in part due to calcineurin inhibitor-induced renal vasoconstriction, through activation of the intrarenal renin-angiotensin system, TGF-beta1 upregulation and TGF-beta1 gene polymorphisms. Overproduction of angiotensin II, associated with angiotensin-converting-enzyme genotype, might be associated with poor prognosis and pharmacological factor gene polymorphisms, and may contribute to variation of calcineurine inhibitor exposure in the kidney. Strategies to prevent renal dysfunction include reducing calcineurine inhibitor exposure or delaying calcineurine inhibitor administration from the early post-transplant period. Calcium channel blockers and angiotensin-converting-enzyme inhibitors, blockade of angiotensin II, or anti-TGF-beta1 antibodies might limit nephrotoxicity. No accurate marker can predict the potential of renal lesions to develop. Lowering calcineurine inhibitors levels with immunosuppressive agents that are either less nephrotoxic or non-nephrotoxic should be formally studied. Of high interest is the impact of genetic polymorphism on the development of renal dysfunction.

Renal protective role of atrial natriuretic peptide in acute sodium overload-induced inflammatory response

BACKGROUND

The present study was performed to explore the effect of exogenous infusions of atrial natriuretic peptide (ANP) on the early inflammatory response during acute sodium overload in normal rats.

METHODS

Sprague Dawley rats were exposed to acute sodium overload (Na 1.5 M). Nonhypotensive doses of ANP (1 and 5 microg x kg(-1) x h(-1)) were infused simultaneously with sodium or after sodium infusion in order to evaluate prevention or reversion of the inflammatory response, respectively. We determined inflammation markers in renal tissue by immunohistochemistry.

RESULTS

Creatinine clearance was not reduced in any case. Sodium tubular reabsorption increased after sodium overload (334.3 +/- 18.7 vs. control 209.6 +/- 27.0 mEq x min(-1), p < 0.05) without changes in mean arterial pressure. This increase was prevented (228.9 +/- 26.4; p < 0.05) and reversed (231.5 +/- 13.9; p < 0.05) by ANP-5 microg x kg(-1) x h(-1). Sodium overload increased the expression of: RANTES (38.4.3 +/- 0.8 vs. 2.9 +/- 0.6%, p < 0.001), transforming-growth-factor-beta(1) (35.3 +/- 1.0 vs. 5.0 +/- 0.7%, p < 0.001), alpha-smooth muscle actin (15.6 +/- 0.7 vs. 3.1 +/- 0.3%, p < 0.001), NF-kappaB (9.4 +/- 1.3 to 2.2 +/- 0.5 cells/mm(2), p < 0.001), HIF-1alpha (38.2 +/- 1.7 to 8.4 +/- 0.8 cells/mm(2), p < 0.001) and angiotensin II (35.9 +/- 1.3 to 8.2 +/- 0.5%, p < 0.001). ANP-5 microg x kg(-1) x h(-1) prevented and reversed inflammation: RANTES (9.2 +/- 0.5 and 6.9 +/- 0.7, p < 0.001); transforming growth factor-beta(1) (13.2 +/- 0.7 and 10.2 +/- 0.5, p < 0.001) and alpha-smooth muscle actin (4.1 +/- 0.4 and 5.2 +/- 0.4, p < 0.001). Both prevention and reversion by ANP were associated with downregulation of NF-kappaB (3.2 +/- 0.4 and 2.8 +/- 0.5, p < 0.001) and angiotensin II (8.2 +/- 0.5 and 9.1 +/- 0.7, p < 0.001) and diminished hypoxia evaluated through HIF-1alpha expression (8.4 +/- 0.8 and 8.8 +/- 0.7, p < 0.001).

CONCLUSION

Our study provides evidence supporting a protective role of ANP in both prevention and reversion of renal inflammation in rats with acute sodium overload.

AT1 antagonist modulates activin-like kinase 5 and TGF-beta receptor II in the developing kidney

Previous studies by our group have demonstrated that angiotensin-converting enzyme (ACE) inhibition in the developing kidney modulates transforming growth factor-beta receptors. Blocking of angiotensin II (ANG II) mainly through angiotensin II type 1 receptor (AT1) has been implicated in mediating this ACE inhibition. The present study was designed to investigate the effects of an AT1 antagonist, losartan, on transforming growth factor-beta1 (TGF-beta1), TGF-beta receptor I [TbetaRI, activin-like kinase (ALK)-1, ALK-5], TGF-beta receptor II (TbetaRII), and alpha-smooth muscle actin (alpha-SMA) expression in the developing kidney. Newborn rat pups were treated with losartan (30 mg/kg per day) or normal saline for 7 days. Kidneys were removed for immunohistochemistry, reverse transcription polymerase chain reaction (PCR), and Western blotting of TGF-beta1, ALK-1, ALK-5, TbetaRII, and alpha-SMA. Renal ALK-5 and TbetaRII protein expressions in the losartan-treated group were found to be significantly increased (P<0.05), whereas TGF-beta1, ALK-1, and alpha-SMA protein expressions were not changed by losartan treatment. The losartan-treated group also showed significantly increased mean tubular diameter and interstitial area of the kidney (P<0.05). These results suggest that AT1 inhibition in the developing kidney impairs renal growth and development and modulates the expression of ALK-5 and TbetaRII.

Angiotensin II compartmentalization within the kidney: effects of salt diet and blood pressure alterations

PURPOSE OF REVIEW

All components of the renin-angiotensin-aldosterone system are present within the kidney. Renin, renin receptor, angiotensinogen and angiotensin AT1 and AT2 receptor and aldosterone synthase messenger RNA and protein are present in close proximity to the renal vasculature and tubules. The interaction between the different components of the renin-angiotensin-aldosterone system determines the level of activity of this system and in turn may influence the regulation of blood pressure and renal sodium handling.

RECENT FINDINGS

Angiotensin through the stimulation of its subtype AT2 receptor regulates sodium excretion, renin synthesis and secretion. Aldosterone synthase mRNA and protein are expressed in glomeruli, renal vasculature and tubules, and are regulated by angiotensin AT1 receptor, diabetes and salt. Although aldosterone is known to influence renal tubular channels with the subsequent enhancement of sodium reabsorption, it is not clear if the renally produced aldosterone also influences renal sodium handling or blood pressure regulation. In addition, angiotensin II influences kidney function and structure through the stimulation of renal inflammation. New data suggest that the renal AT1 receptor plays an important role in the determination of blood pressure levels, and this effect is unique and non-redundant in the actions of extrarenal AT1 receptors.

SUMMARY

The finding of new functions and components of the renin-angiotensin-aldosterone system clearly adds new knowledge to our understanding of how angiotensin II influences the kidney and blood pressure.

Attenuation of interstitial inflammation and fibrosis by recombinant human erythropoietin in chronic cyclosporine nephropathy

BACKGROUND

Evidence suggests that recombinant human erythropoietin (rHuEPO) protects neurons and cardiomyocytes from acute insults. We investigated the protective effect of rHuEPO on cyclosporine (CsA)-induced renal injury.

METHODS

CsA (15 mg/kg/day) was given to rats for 1 or 4 weeks, and rHuEPO was concurrently administered at a dose of 100 units/kg (thrice weekly). Effects of rHuEPO on CsA-induced renal injury were evaluated with tubulointerstitial fibrosis (TIF) score, macrophage infiltration, expression of proinflammatory and profibrotic cytokines, and apoptotic cell death.

RESULTS

Administration of rHuEPO decreased TIF score and the number of macrophages, which increased significantly in CsA-treated rat kidneys. At the molecular level, rHuEPO treatment decreased proinflammatory mediators (osteopontin and C-reactive protein) and profibrotic mediators (transforming growth factor-beta1 and transforming growth factor-beta1-inducible gene-h3). Increased apoptotic cell death in CsA-treated rat kidneys was significantly decreased with rHuEPO cotreatment, and apoptosis-related genes were regulated in favor of cell survival (increased Bcl-2 and suppressed caspase-3).

CONCLUSION

rHuEPO has a renoprotective effect against chronic CsA-induced renal injury.