Effect of high dose ramipril with or without indomethacin on glomerular selectivity

Treatment of membranous nephropathy: time for a paradigm shift

In patients with membranous nephropathy, alkylating agents (cyclophosphamide or chlorambucil) alone or in combination with steroids achieve remission of nephrotic syndrome more effectively than conservative treatment or steroids alone, but can cause myelotoxicity, infections, and cancer. Calcineurin inhibitors can improve proteinuria, but are nephrotoxic. Most patients relapse after treatment withdrawal and can become treatment dependent, which increases the risk of nephrotoxicity. The discovery of nephritogenic autoantibodies against podocyte M-type phospholipase A2 receptor (PLA₂R) and thrombospondin type-1 domain- containing protein 7A (THSD7A) antigens provides a clear pathophysiological rationale for interventions that specifically target B-cell lineages to prevent antibody production and subepithelial deposition. The anti-CD20 monoclonal antibody rituximab is safe and achieves remission of proteinuria in approximately two-thirds of patients with membranous nephropathy. In those with PLA₂R-related disease, remission can be predicted by anti-PLA₂R antibody depletion and relapse by antibody re-emergence into the circulation. Thus, integrated evaluation of serology and proteinuria could guide identification of affected patients and treatment with individually tailored protocols. Nonspecific and toxic immunosuppressive regimens will fall out of use. B-cell modulation by rituximab and second-generation anti-CD20 antibodies (or plasma cell-targeted therapy in anti-CD20 resistant forms of disease) will lead to a novel therapeutic paradigm for patients with membranous nephropathy.

Radiocontrast-Induced Acute Renal Failure

The intravascular administration of iodinated radiocontrast media can lead to acute renal dysfunction. Even small changes in renal function have been associated with increased morbidity and mortality, making the prevention of radiocontrast nephropathy of paramount importance. This review summarizes the principal risk factors for radiocontrast nephropathy and evidence-based preventive strategies that should be used to limit its occurrence. Risk factors for radiocontrast nephropathy include preexistent kidney disease, diabetes mellitus, dose of radiocontrast used, advanced congestive heart failure, and intravascular volume depletion. Proven preventive measures include volume expansion with intravenous saline or sodium bicarbonate and the use of low-osmolar or iso-osmolar radiocontrast media. Studies evaluating N-acetylcysteine have been conflicting, with meta-analyses suggesting a small beneficial effect. Studies of other pharmacologic agents have not demonstrated clinical benefit.

Indomethacin reduces glomerular and tubular damage markers but not renal inflammation in chronic kidney disease patients: a post-hoc analysis

Under specific conditions non-steroidal anti-inflammatory drugs (NSAIDs) may be used to lower therapy-resistant proteinuria. The potentially beneficial anti-proteinuric, tubulo-protective, and anti-inflammatory effects of NSAIDs may be offset by an increased risk of (renal) side effects. We investigated the effect of indomethacin on urinary markers of glomerular and tubular damage and renal inflammation. We performed a post-hoc analysis of a prospective open-label crossover study in chronic kidney disease patients (n = 12) with mild renal function impairment and stable residual proteinuria of 4.7±4.1 g/d. After a wash-out period of six wks without any RAAS blocking agents or other therapy to lower proteinuria (untreated proteinuria (UP)), patients subsequently received indomethacin 75 mg BID for 4 wks (NSAID). Healthy subjects (n = 10) screened for kidney donation served as controls. Urine and plasma levels of total IgG, IgG4, KIM-1, beta-2-microglobulin, H-FABP, MCP-1 and NGAL were determined using ELISA. Following NSAID treatment, 24 h -urinary excretion of glomerular and proximal tubular damage markers was reduced in comparison with the period without anti-proteinuric treatment (total IgG: UP 131[38–513] vs NSAID 38[17–218] mg/24 h, p<0.01; IgG4: 50[16–68] vs 10[1–38] mg/24 h, p<0.001; beta-2-microglobulin: 200[55–404] vs 50[28–110] ug/24 h, p = 0.03; KIM-1: 9[5]–[14] vs 5[2]–[9] ug/24 h, p = 0.01). Fractional excretions of these damage markers were also reduced by NSAID. The distal tubular marker H-FABP showed a trend to reduction following NSAID treatment. Surprisingly, NSAID treatment did not reduce urinary excretion of the inflammation markers MCP-1 and NGAL, but did reduce plasma MCP-1 levels, resulting in an increased fractional MCP-1 excretion. In conclusion, the anti-proteinuric effect of indomethacin is associated with reduced urinary excretion of glomerular and tubular damage markers, but not with reduced excretion of renal inflammation markers. Future studies should address whether the short term glomerulo- and tubulo-protective effects as observed outweigh the possible side-effects of NSAID treatment on the long term.

Mineralocorticoid receptor blockers and chronic kidney disease

The increasing prevalence of chronic kidney disease (CKD) and the public health initiatives for detection and slowing its progression have placed special emphasis on controlling proteinuria and the renin-angiotensin-aldosterone system (RAAS). In addition to the traditional blockers of angiotensin-converting enzyme and angiotensin receptors, mineralocorticoid receptor blockers (MRBs) have come into focus as anti-proteinuric agents with moderate anti-hypertensive effects. The beneficial effects of MRBs on mortality in patients with cardiac disease have been well described. We review the role of aldosterone in end-organ damage, the rationales for using MRBs as adjuncts to angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in treating CKD, and the adverse effects that may occur when these agents are used in combination. Suggestions are included for avoiding serious adverse events in CKD patients treated with MRBs. There is a clearly defined need for prospective outcome studies focused on cardiovascular mortality as well as progression of CKD in patients treated with MRBS and other inhibitors of the RAAS.

Investigational drugs for diabetic nephropathy

BACKGROUND

Diabetic nephropathy is one of the main causes of end-stage renal disease (ESRD) and is associated with elevated cardiovascular morbidity and mortality.

OBJECTIVE

Current renoprotective treatments for diabetic nephropathy include strict glycemic and optimal blood pressure control, proteinuria/albuminuria reduction and the use of renin-angiotensin-aldosterone system (RAAS) blocking agents. However, the renoprotection provided by these treatments is only partial, calling for more effective approaches.

METHODS

This review examines emerging strategies for the treatment of diabetic nephropathy, including aggressive RAAS blockade, statins, glitazones, ruboxistaurin, and other promising agents.

RESULTS/CONCLUSIONS

In diabetic patients with overt nephropathy, multipharmacological interventions represent a promising way to prevent progression to ESRD. Results of ongoing trials are needed to establish whether the current standard of care of diabetic nephropathy might be improved with these new strategies.

Regression of glomerular injury by losartan in experimental diabetic nephropathy

Many features of chronic kidney disease may be reversed, but it is unclear whether advanced lesions, such as adhesions of sclerotic glomerular tufts to Bowman's capsule (synechiae), can resolve during treatment. We previously showed, using a renal ablation model, that the renoprotective effect of the AT-1 receptor blocker, losartan, is dose-dependent. Here we determined if moderate and advanced glomerular lesions, associated with streptozotocin-induced diabetes, regress with conventional or high-dose losartan treatment. Using daily insulin injection for 10 months, we maintained diabetic adult male Munich-Wistar rats in a state of moderate hyperglycemia. Following this period, some rats continued to receive insulin with or without conventional or high-dose losartan for an additional 2 months. Diabetic rats pretreated with insulin for 10 months and age-matched non-diabetic rats served as controls. Mesangial expansion was found in the control diabetic rats and was exacerbated in those rats maintained on only insulin for an additional 2 months. Conventional and high-dose losartan treatments reduced this mesangial expansion and the severity of synechiae lesions below that found prior to treatment; however, the frequency of the latter was unchanged. There was no dose-response effect of losartan. Our results show that regression of mesangial expansion and contraction of sclerotic lesions is feasible in the treatment of diabetes, but complete resolution of advanced glomerulosclerosis may be hard to achieve.

Renoprotection of Optimal Antiproteinuric Doses (ROAD) Study: a randomized controlled study of benazepril and losartan in chronic renal insufficiency

The Renoprotection of Optimal Antiproteinuric Doses (ROAD) study was performed to determine whether titration of benazepril or losartan to optimal antiproteinuric doses would safely improve the renal outcome in chronic renal insufficiency. A total of 360 patients who did not have diabetes and had proteinuria and chronic renal insufficiency were randomly assigned to four groups. Patients received open-label treatment with a conventional dosage of benazepril (10 mg/d), individual uptitration of benazepril (median 20 mg/d; range 10 to 40), a conventional dosage of losartan (50 mg/d), or individual uptitration of losartan (median 100 mg/d; range 50 to 200). Uptitration was performed to optimal antiproteinuric and tolerated dosages, and then these dosages were maintained. Median follow-up was 3.7 yr. The primary end point was time to the composite of a doubling of the serum creatinine, ESRD, or death. Secondary end points included changes in the level of proteinuria and the rate of progression of renal disease. Compared with the conventional dosages, optimal antiproteinuric dosages of benazepril and losartan that were achieved through uptitration were associated with a 51 and 53% reduction in the risk for the primary end point (P = 0.028 and 0.022, respectively). Optimal antiproteinuric dosages of benazepril and losartan, at comparable BP control, achieved a greater reduction in both proteinuria and the rate of decline in renal function compared with their conventional dosages. There was no significant difference for the overall incidence of major adverse events between groups that were given conventional and optimal dosages in both arms. It is concluded that uptitration of benazepril or losartan against proteinuria conferred further benefit on renal outcome in patients who did not have diabetes and had proteinuria and renal insufficiency.

Permselective dysfunction of podocyte-podocyte contact upon angiotensin II unravels the molecular target for renoprotective intervention

Ameliorating the function of the glomerular barrier to circulating proteins by blocking angiotensin II (Ang II) translates into less risk of progression toward end-stage renal failure in diabetic and nondiabetic nephropathies. However, the mechanisms underlying this barrier protection are not clear. Specialized contacts between adjacent podocytes are major candidate targets, and the actin cytoskeleton is emerging as a regulatory element. Here, we present data demonstrating that Ang II induced reorganization of F-actin fibers and redistribution of zonula occludens-1 (ZO-1) that is physically associated with actin in murine podocytes. These effects were paralleled by increased albumin permeability across podocyte monolayers. The F-actin stabilizer jasplakinolide prevented both ZO-1 redistribution and albumin leakage, suggesting that actin cytoskeleton rearrangement is instrumental to podocyte permselective dysfunction induced by Ang II. Changes in both F-actin and ZO-1 patterns were confirmed in glomeruli of rat isolated perfused kidneys on short infusion of Ang II, leading to increased protein excretion. Podocyte dysfunction was mediated by Ang II type 1 receptor and was partly dependent on Src kinase-phospholipase C activation. These data demonstrate that strategies aimed at stabilizing podocyte-podocyte contacts and targeting the relevant intracellular signal transduction are crucial to renoprotection.

Changes in glomerular perm-selectivity induced by angiotensin II imply podocyte dysfunction and slit diaphragm protein rearrangement

Molecular mechanisms governing the loss of glomerular membrane perm selectivity during progression of proteinuric kidney diseases are so far poorly defined. Discovery of the proteins of the podocyte slit diaphragm, including the nephrin-CD2AP-podocin complex, has represented a major breakthrough in understanding the crucial role of the glomerular epithelial layer in the pathogenesis of proteinuria in human congenital disorders. A number of studies have tried to address the role of nephrin in acquired proteinuric disorders with conflicting results. In human diabetic nephropathy a defect of nephrin gene and protein expression has been consistently reported, which translates in profound changes of filtration slit ultrastructural architecture. The exclusive effect of angiotensin II inhibitors of restoring deficient nephrin expression in proteinuric diseases underlines a close interaction between angiotensin II and podocyte proteins and indicates a fresh way to look at the renoprotective properties of these molecules.

Antihypertensive and antiproteinuric efficacy of ramipril in children with chronic renal failure

BACKGROUND

While the antihypertensive and renoprotective potency of angiotensin-converting enzyme (ACE) inhibitors is well-established in adults with hypertension and/or chronic renal failure, little experience exists in pediatric chronic kidney disease.

METHODS

As part of a prospective assessment of the renoprotective efficacy of ACE inhibition and intensified blood pressure (BP) control, 397 children (ages 3 to 18 years) with chronic renal failure [CRF; glomerular filtration rate (GFR) 11 to 80 mL/min/1.73 m2] and elevated or high-normal BP received ramipril (6 mg/m2) following a 6-month run-in period including a two-month washout of any previous ACE inhibitors. Drug efficacy was assessed by two monthly office BP and proteinuria assessments, and by ambulatory BP monitoring at start and after 6 months of treatment.

RESULTS

In the 352 patients completing six months of treatment, 24-hour mean arterial pressure (MAP) had decreased by a mean of 11.5 mm Hg (-2.2 SDS) in initially hypertensive subjects, but only by 4.4 mm Hg (-0.8 SDS) in patients with initially normal BP. A linear correlation was found between MAP at baseline and the change of MAP during treatment (r= 0.51; P < 0.0001). The antihypertensive response was independent of changes in concomitant antihypertensive medication or underlying renal disease. BP was reduced with equal efficacy during day- and nighttime. Urinary protein excretion was reduced by 50% on average, with similar relative efficacy in patients with hypo/dysplastic nephropathies and glomerulopathies. The magnitude of proteinuria reduction depended on baseline proteinuria (r= 0.32, P < 0.0001), and was correlated with the antihypertensive efficacy of the drug (r= 0.22, P < 0.001). The incidence of rapid rises in serum creatinine and progression to end-stage CRF during treatment did not differ from the pretreatment observation period. Mean serum potassium increased by 0.3 mmol/L. Ramipril was discontinued in three patients due to symptomatic hypotension or hyperkalemia. Hemoglobin levels decreased by 0.6 g/dL in the first two treatment months and remained stable thereafter.

CONCLUSION

Ramipril appears to be an effective and safe antihypertensive and antiproteinuric agent in children with CRF-associated hypertension. The BP lowering and antiproteinuric effects are greatest in severely hypertensive and proteinuric children.

Management of Glomerular Proteinuria: A Commentary

ABSTRACT. It is widely accepted that proteinuria reduction is an appropriate therapeutic goal in chronic proteinuric kidney disease. Based on large randomized controlled clinical trials (RCT), ACE inhibitor (ACEI) and angiotensin receptor blocker (ARB) therapy have emerged as the most important antiproteinuric and renal protective interventions. However, there are numerous other interventions that have been shown to be antiproteinuric and, therefore, likely to be renoprotective. Unfortunately testing each of these antiproteinuric therapies in RCT is not feasible. The nephrologist has two choices: restrict antiproteinuric therapies to those shown to be effective in RCT or expand the use of antiproteinuric therapies to include those that, although unproven, are plausibly effective and prudent to use. The goal of this work is to provide the documentation needed for the nephrologist to choose between these strategies. This work describes 25 separate interventions that are either antiproteinuric or may block injurious mechanisms of proteinuria. Each intervention is assigned a level of recommendation (Level 1 is the highest; Level 3 is the lowest) according to the strength of the evidence supporting its antiproteinuric and renoprotective efficacy. Pathophysiologic mechanisms possibly involved are also discussed. The number of interventions at each level of recommendation are: Level 1, n = 7; Level 2, n = 9; Level 3, n = 9. Our experience indicates that we can achieve in most patients the majority of Level 1 and many of the Level 2 and 3 recommendations. We suggest that, until better information becomes available, a broad-based, multiple-risk factor intervention to reduce proteinuria can be justified in those with progressive nephropathies. This work is intended primarily for clinical nephrologists; therefore, each antiproteinuria intervention is described in practical detail.

Maximal suppression of renin-angiotensin system in nonproliferative glomerulonephritis

BACKGROUND

Elimination of residual proteinuria is the novel target in renoprotection; nevertheless, whether a greater suppression of renin-angiotensin system (RAS) effectively improves the antiproteinuric response in patients with moderate proteinuria remains ill-defined.

METHODS

We evaluated the effects of maximizing RAS suppression on quantitative and qualitative proteinuria in ten patients with stable nonnephrotic proteinuria (2.55 +/- 0.94 g/24 hours) due to primary nonproliferative glomerulonephritis (NPGN), and normal values of creatinine clearance (103 +/- 17 mL/min). The study was divided in three consecutive phases: (1) four subsequent 1-month periods of ramipril at the dose of 2.5, 5.0, 10, and 20 mg/day; (2) 2 months of ramipril 20 mg/day + irbesartan 300 mg/day; and (3) 2 months of irbesartan 300 mg/day alone.

RESULTS

Maximizing RAS suppression was not coupled with any major effect on renal function and blood pressure; conversely, a significant decrement in hemoglobin levels, of 0.8 g/dL on average, was observed during up-titration of ramipril dose. The 2.5 mg dose of ramipril significantly decreased proteinuria by 29%. Similar changes were detected after irbesartan alone (-28%). The antiproteinuric effect was not improved either by the higher ramipril doses (-30% after the 20 mg dose) or after combined treatment (-33%). The reduction of proteinuria led to amelioration of the markers of tubular damage, as testified by the significant decrement of alpha 1 microglobulin (alpha 1m) excretion and of the tubular component of proteinuria at sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

CONCLUSION

In nonnephrotic NPGN patients, standard doses of either ramipril or irbesartan lead to significant reduction of residual proteinuria and amelioration of the qualitative features suggestive of tubular damage. The enhancement of RAS suppression up to the maximal degree does not improve the antiproteinuric response and is coupled with a decrement of hemoglobin levels.