Line Aas Mortensen

Key Points: Spironolactone is safe for kidney transplant patients. Spironolactone reduces kidney function by an acute effect, whereafter it remains stable. Spironolactone does not affect the progression of interstitial fibrosis in protocol biopsies. Background: Long-term kidney allograft survival is hampered by progressive interstitial fibrosis and tubular atrophy. The SPIREN trial tested the hypothesis that the mineralocorticoid receptor antagonist spironolactone stabilizes kidney function and attenuates glomerular barrier injury in kidney transplant patients treated with calcineurin inhibitors. Methods: We conducted a randomized, placebo-controlled, double-blind clinical trial including 188 prevalent kidney transplant patients. Patients were randomized to spironolactone or placebo for 3 years. GFR was measured along with proteinuria and kidney fibrosis. The primary end point was change in measured GFR. Secondary outcomes were 24-hour proteinuria, kidney allograft fibrosis, and cardiovascular events. Measured GFRs, 24-hour proteinuria, and BP were determined yearly. Kidney biopsies were collected at baseline and after 2 years (n=48). Fibrosis was evaluated by quantitative stereology and classified according to Banff. Results: The groups were comparable at baseline except for slightly older allografts in the spironolactone group. Spironolactone reduced measured GFRs (up to –7.6 [95% confidence interval, −10.9 to −4.3] ml/min compared with placebo) independently of time since transplantation and BP with no effect on the kidney function curve over time and reduced 24-hour proteinuria after 1 year. There was no significant effect of spironolactone on the development of interstitial fibrosis. Conclusions: Spironolactone added to standard therapy for 3 years in kidney transplant patients did not improve kidney function, long-term proteinuria, or interstitial fibrosis. Clinical Trial registration number: NCT01602861.

Kidney transplantation is associated with increased risk of cardiovascular morbidity. Interleukin (IL)-17A mediates kidney injury. Aldosterone promotes T helper 17 lymphocyte differentiation and IL-17A production through the mineralocorticoid receptor. In this exploratory, post hoc substudy, it was hypothesized that a 1-yr intervention with the mineralocorticoid receptor antagonist spironolactone lowers IL-17A and related cytokines and reduces epithelial injury in kidney transplant recipients. Plasma and urine samples were obtained from kidney transplant recipients from a double-blind randomized clinical trial testing spironolactone (n = 39) versus placebo (n = 41). Plasma concentrations of cytokines interferon-γ, IL-17A, tumor necrosis factor-α, IL-6, IL-1β, and IL-10 were determined before and after 1-yr treatment. Urine calbindin-to-creatinine, clusterin-to-creatinine, kidney injury molecule-1-to-creatinine, osteoactivin-to-creatinine, trefoil factor 3 (TFF3)-to-creatinine, and VEGF-to-creatinine ratios were analyzed. Blood pressure and plasma aldosterone concentration at inclusion did not relate to plasma cytokines and injury markers expect for urine TFF3-to-creatinine ratios that correlated positively to blood pressure. None of the cytokines changed in plasma after spironolactone intervention. Plasma IL-17A increased in the placebo-treated group. Spironolactone induced an increase in plasma K⁺ (0.4 ± 0.4 mmol/L). This increase did not correlate with plasma IL-17A or urine calbindin and TFF3 changes. Ongoing treatment at inclusion with angiotensin-converting enzyme inhibitor and/or ANG II receptor blockers was not associated with changed levels of IL-17A and injury markers and had no effect on the response to spironolactone. Urinary calbindin and TFF3 decreased in the spironolactone-treated group with no difference in between-group analyses. In conclusion, irrespective of ongoing ANG II inhibition, spironolactone has no effect on plasma IL-17A and related cytokines or urinary injury markers in kidney transplant recipients. NEW & NOTEWORTHY The mineralocorticoid receptor antagonist spironolactone had no direct anti-inflammatory effects on prohypertensive interleukin-17A or distal nephron epithelial injury markers in kidney transplant recipients.

Nephrogenic diabetes insipidus (NDI) is characterized by renal resistance to the antidiuretic hormone arginine vasopressin (AVP), which leads to polyuria, plasma hyperosmolarity, polydipsia, and impaired quality of living. Inherited forms are caused by X-linked loss-of-function mutations in the gene encoding the vasopressin 2 receptor (V2R) or autosomal recessive/dominant mutations in the gene encoding aquaporin 2 (AQP2). A common acquired form is lithium-induced NDI. AVP facilitates reabsorption of water through increased abundance and insertion of AQP2 in the apical membrane of principal cells in the collecting ducts. In X-linked NDI, V2R is dysfunctional, which leads to impaired water reabsorption. These patients have functional AQP2, and thus the challenge is to achieve AQP2 membrane insertion independently of V2R. The current treatment is symptomatic and is based on distally acting diuretics (thiazide or amiloride) and cyclooxygenase inhibitors (indomethacin). This mini-review covers published data from trials in preclinical in vivo models and a few human intervention studies to improve NDI by more causal approaches. Promising effects on NDI in preclinical studies have been demonstrated by the use of pharmacological approaches with secretin, Wnt5a, protein kinase A agonist, fluconazole, prostaglandin E₂ EP2 and EP4 agonists, statins, metformin, and soluble prorenin receptor agonists. In patients, only casuistic reports have evaluated the effect of statins, phosphodiesterase inhibitors (rolipram and sildenafil), and the guanylate cyclase stimulator riociguat without amelioration of symptoms. It is concluded that there is currently no established intervention that causally improves symptoms or quality of life in patients with NDI. There is a need to collaborate to improve study quality and conduct formal trials.

Renal transplantation is the preferred treatment of end stage renal disease, but allograft survival is limited by the development of interstitial fibrosis and tubular atrophy in response to various stimuli. Much effort has been put into identifying new protein markers of fibrosis to support the diagnosis. In the present work, we performed an in-depth quantitative proteomics analysis of allograft biopsies from 31 prevalent renal transplant patients and correlated the quantified proteins with the volume fraction of fibrosis as determined by a morphometric method. Linear regression analysis identified four proteins that were highly associated with the degree of interstitial fibrosis, namely Coagulation Factor XIII A chain (estimate 18.7, adjusted p < 0.03), Uridine Phosphorylase 1 (estimate 19.4, adjusted p < 0.001), Actin-related protein 2/3 subunit 2 (estimate 34.2, adjusted p < 0.05) and Cytochrome C Oxidase Assembly Factor 6 homolog (estimate −44.9, adjusted p < 0.002), even after multiple testing. Proteins that were negatively associated with fibrosis (p < 0.005) were primarily related to normal metabolic processes and respiration, whereas proteins that were positively associated with fibrosis (p < 0.005) were involved in catabolic processes, cytoskeleton organization and the immune response. The identified proteins may be candidates for further validation with regards to renal fibrosis. The results support the notion that cytoskeleton organization and immune responses are prevalent processes in renal allograft fibrosis.

Kidney transplantation is associated with increased cardiovascular risk. Endothelial dysfunction and vascular inflammation contribute to negative outcome. In experimental models, mineralocorticoid receptor antagonists improved endothelial function and reduced inflammation. The present study tested the hypothesis that the mineralocorticoid receptor antagonist spironolactone improves endothelial function and reduces vascular inflammation in renal transplant patients. Eighty prevalent renal transplant patients from an ongoing, double-blind randomized placebo-controlled trial were included. Paired plasma samples before and after 1 yr of treatment ( n = 39 in the spironolactone-treated group and 41 in the placebo-treated group) were used to determine markers of endothelial dysfunction (nitrite, nitrate, cGMP, arginine, citrulline, ornithine, asymmetric dimethylarginine, symmetric dimethylarginine, N^G-monomethyl-l-arginine, von Willebrand factor, tissue-type plasminogen activator antigen, and plasminogen activator inhibitor 1 antigen) and markers of inflammation (intercellular adhesion molecule, vascular adhesion molecule, high-sensitivity C-reactive protein, and serum amyloid protein A). The median time since the transplantation was 4.6 (0.12–22.3) yr in the spironolactone-treated group and 2.1 (0.17–13.9) yr in the placebo-treated group ( P > 0.05). Spironolactone increased plasma aldosterone ( P < 0.001) and K⁺ ( P < 0.001). Blood pressure did not change significantly. No significant differences were detected between groups in any of the measured markers of endothelial dysfunction or inflammation except in the subgroup analysis of patients with diabetes, where spironolactone decreased nitrite compared with placebo. In this study, mineralocorticoid receptor antagonism did not improve biomarkers of endothelial dysfunction or vascular inflammation in prevalent renal transplant patients. Further studies are needed to evaluate the potential beneficial effect of early or late mineralocorticoid receptor antagonism on vascular outcomes in renal transplant patients.

Calcineurin inhibitor induced nephrotoxicity contributes to late allograft failure in kidney transplant patients. Evidence points towards aldosterone to play a role in the development of fibrosis in multiple organs. Animal studies have indicated a beneficial effect of mineralocorticoid receptor antagonists preventing calcineurin inhibitor induced nephrotoxicity. Only few studies have explored this effect in humans. The objective of this study is to evaluate the effect of spironolactone on glomerular filtration rate and fibrosis in kidney transplant patients. Prospective, double-blind, randomized, clinical trial including 170 prevalent kidney transplant patients. Patients are randomized to spironolactone 25–50 mg/day or placebo for three years. Primary outcome is glomerular filtration rate evaluated by chrome-EDTA clearance. Secondary outcomes are 24-h protein excretion, amount of interstitial fibrosis in renal allograft biopsies, and cardiovascular events. As an exploratory outcome, we aim to identify markers of fibrosis in blood and urine. Long term allograft survival remains a key issue in renal transplantation, partly due to calcineurin inhibitor induced nephrotoxicity. Evidence from animal- and small human studies indicate a beneficial effect of mineralocorticoid receptor antagonism on renal function and fibrosis. This study aims to test this hypothesis in a sufficiently powered randomized clinical trial. Results might influence the future management of long term allograft survival in renal transplantation. ClinicalTrials.gov identifier (05/17/2012): NCT01602861 . EudraCT number (05/31/2011): 2011–002243-98.

Calcineurin inhibitors have markedly reduced acute rejection rates in renal transplantation, thus significantly improved short-term outcome. The beneficial effects are, however, tampered by acute and chronic nephrotoxicity leading to interstitial fibrosis and tubular atrophy, which impairs long-term allograft survival. The mineralocorticoid hormone aldosterone induces fibrosis in numerous organs, including the kidney. Evidence from animal models suggests a beneficial effect of aldosterone antagonism in reducing calcineurin inhibitor-induced nephrotoxicity. This review summarizes current evidence of mineralocorticoid receptor antagonism in animal models of calcineurin inhibitor-induced nephrotoxicity and the results from studies of mineralocorticoid antagonism in renal transplant patients.