Angiotensin converting enzyme inhibitor therapy in children with Alport syndrome: effect on urinary albumin, TGF-beta, and nitrite excretion

New therapeutic options for Alport syndrome

Alport syndrome (AS) is the most frequent inherited kidney disease after autosomal dominant polycystic kidney disease. It has three different patterns of inheritance-autosomal dominant, autosomal recessive and X-linked-which in part explains the wide spectrum of disease, ranging from isolated microhaematuria to end-stage renal disease early in life. The search for a treatment for AS is being pursued vigorously, not only because of the obvious unmet need but also because AS is a rare disease and any drug approved will have an orphan drug designation with its various benefits. Moreover, AS patients are quite young with very few comorbidities, which facilitates clinical trials. This review identifies the particularities of each pattern of inheritance but focuses mainly on new drugs or therapeutic targets for the disease. Most treatment-related investigations are directed not at the main abnormality in AS, namely collagen IV composition, but rather at the associated inflammation and fibrosis. Thus, AS may serve as a proof of concept for numerous drugs of potential value in many diseases that cause chronic kidney disease.

RAAS inhibition and the course of Alport syndrome

Alport syndrome (AS) is a hereditary progressive glomerulonephritis with a high life-time risk for end-stage renal disease (ESRD). Most patients will reach ESRD before the age of 30 years, while a subset of them with milder mutations will do so at older ages, even after 50 years. Frequent extrarenal manifestations are hearing loss and ocular abnormalities. AS is a genetically heterogeneous collagen IV nephropathy, with 85% of the cases caused by mutations in the X-linked COL4A5 gene and the rest by homozygous or compound heterozygous mutations in either the COL4A3 or the COL4A4 gene on chromosome 2q36-37. There is no radical cure for the disease and attempts to use various stem cell therapies in animal models have been met with ambiguous success. However, effective treatment has been accomplished with pharmacological intervention at the renin-angiotensin-aldosterone system (RAAS), first in animal models of AS and more recently in humans. Angiotensin converting enzyme inhibitors (ACEis) and angiotensin receptor blockers (ARBs) have been shown to significantly delay the progression of chronic kidney disease and the onset of ESRD. Also, renin inhibitors and aldosterone blockade were used with positive results, while the combination of ACEis and ARBs was met with mixed success. An important study, the EARLY-PROTECT, aims at evaluating the efficacy of ACEis when administered very early on in children with AS. Novel therapies are also tested experimentally or are under design in animal models by several groups, including the use of amniotic fluid stem cells and synthetic chaperones.

Long-term treatment by ACE inhibitors and angiotensin receptor blockers in children with Alport syndrome

BACKGROUND

The aim of this study was to analyze the long-term efficacy and safety of angiotensin-converting enzyme inhibitor (ACEi) and ACEi + angiotensin receptor blocker (ARB) treatments in a cohort of children with Alport syndrome (AS).

METHODS

This was a respective review of 79 Chinese children with AS who received ACEi alone or combined ACEi + ARB therapy.

RESULTS

The mean age of the pediatric patients with AS at onset of treatment was 8.6 ± 4.1 (range 1.5-16.3) years. The mean duration of follow-up was 2.5 ± 1.8 (range 0.5-7.8) years. For analysis, we separated the children into three groups according to proteinuria level before treatment, namely, <25, 25-50, and ≥50 mg/kg/day, respectively; after 1 year of treatment the proteinuria had decreased from 11.0 to 9.7 mg/kg/day, from 34.6 to 15.2 mg/kg/day, and from 73.0 to 50.0 mg/kg/day in each group, respectively. Proteinuria decreased significantly during the first 2 years of treatment and was stable from the third to fifth years of treatment. There was no statistically significant difference in the antiproteinuric effect of the ACEi and ACEi + ARB treatments in patients with severe or less severe mutations after 1 year of therapy. Five children stopped the ACEi + ARB treatment due to a decline in creatinine clearance.

CONCLUSION

Our findings demonstrate that early and long-term ACEi and ARB treatments in children with AS is efficient and well tolerated. The antiproteinuric effect of ACEi and ARB is of equal value in children with severe and less severe mutations in the COL4An gene.

Alport syndrome: the effects of spironolactone on proteinuria and urinary TGF-β1

BACKGROUND

Alport syndrome (AS) is a progressive hereditary glomerular disease. Recent data indicate that aldosterone promotes fibrosis mediated by the transforming growth factor-β1 (TGF-β1) pathway, which may worsen proteinuria. Spironolactone (SP) antagonizes aldosterone and this study aimed to evaluate the efficacy of SP in reducing proteinuria and urinary TGF-β1 excretion in proteinuric AS patients.

METHODS

The study involved ten children with AS, normal renal function, and persistent proteinuria (>6 months; uPr/uCr ratio >1). SP 25 mg once a day for 6 months was added to existing ACE inhibitor treatment with or without angiotensin-II receptor blockade. Urine and blood samples were examined monthly. Urinary TGF-β1 levels were measured twice before and three times during SP treatment. Plasma renin activity (PRA) and serum aldosterone levels were also measured. In eight patients, uProt/uCreat was also assessed after 9 months and 12 months of SP treatment.

RESULTS

After beginning SP therapy, all patients showed significant decrease in mean uProt/uCreat ratio (1.77 ± 0.8 to 0.86 ± 0.6; p < 0.001) and mean urinary TGF-β1 levels (104 ± 54 to 41 ± 20 pg/mgCreatinine; p < 0.01), beginning after 30 days of treatment and remaining stable throughout SP administration. PRA remain unchanged, and mean serum aldosterone increased from 105 ± 72 pg/ml to 303 ± 156 pg/ml (p < 0.001). The only side effect was gynecomastia in an obese boy. After 1 year of therapy, mean uProt/uCreat remains low (0.82 ± 0.48).

CONCLUSIONS

Addition of SP to ACE-I treatment with or without angiotensin II receptor blokers (ARB) significantly reduced proteinuria. This was mediated by decreased urinary TGF-β1 levels and not associated with major side effects.

Drugs controlling proteinuria of patients with Alport syndrome

BACKGROUND

Proteinuria is one of the risk factors for the progression of renal diseases including Alport syndrome (AS), a hereditary glomerular renal disease. This study aimed to evaluate the efficacy of angiotensin converting enzyme inhibitors (ACEIs) and/or tripterygium, a Chinese herbal medicine widely used in Chinese patients with hematuria and proteinuria, on proteinuria in patients with AS.

METHODS

Twenty-nine children were enrolled into this retrospective study. Patients were divided into 3 therapy groups: ACEI group, tripterygium group, and ACEI plus tripterygium group.

RESULTS

In the 29 children, 23 were male and 6 female. In the ACEI group and the tripterygium group, the effective rate was 87.5% and 25.0%, respectively and in the ACEI plus tripterygium group was 42.9%.

CONCLUSIONS

ACEI is effective in controlling proteinuria of AS patients. Tripterygium should be carefully administered in controlling proteinuria of AS patients.

Add-on therapy with angiotensin II receptor 1 blocker in children with chronic kidney disease already treated with angiotensin-converting enzyme inhibitors

The standard renoprotection is based on the inhibition of the renin-angiotensin system (RAS) by angiotensin convertase inhibitors (ACEi) or angiotensin II receptor 1 blockers (AT1B). The aim of our study was to analyze the effects of the addition of AT1B to ACEi-based renoprotection in children with chronic kidney disease. We examined 11 children with a mean age of 10.5 years (range, 0.5-18 years) with a mean glomerular filtration rate (GFR) of 61+/-61 ml/min/1.73 m(2). In four patients, the primary renal disease was hemolytic uremic syndrome, in three congenital nephrotic syndrome (CNS), in two reflux nephropathy, prune-belly syndrome in one and acute cortical necrosis in one. All patients were treated with complex hypotensive ACEi-based therapy. AT1B losartan was added in a mean dose of 0.9 mg/kg/day. The change in GFR, proteinuria and blood pressure at two 12-month intervals before and after adding AT1B was compared. The results showed that during the 12 months preceding AT1B therapy, there was no change in blood pressure and proteinuria, but the GFR declined in 7 of 11 patients. After the 12th month of add-on therapy with AT1B, there was a significant decrease in both absolute and indexed blood pressure values. Proteinuria decreased in eight patients, did not change in one and increased in two, including one with CNS. The GFR stabilized or increased in eight patients and decreased in three patients with CNS. In 7 of 11 patients, there was a significant, but not threatening increase in serum potassium. In conclusion, add-on renoprotection with AT1B added to ACEi is safe and significantly improves the renoprotective effects of ACEi treatment in children with progressive nephropathies, including patients with advanced CKD.

Effect of fosinopril in children with steroid-resistant idiopathic nephrotic syndrome

We aimed to test if fosinopril reduces urinary protein excretion and alleviates renal tubular damage in normotensive children with steroid-resistant idiopathic nephrotic syndrome (SRINS). We also aimed to evaluate whether there are changes in steady-state blood pressure and serum concentrations of serum angiotensin-converting enzyme (ACE) and plasma renin activity or angiotensin II (AT-II) in children under this treatment. Forty-five normotensive patients with SRINS were randomly divided into two groups. Group I was treated with fosinopril and prednisone for 12 weeks, while group II was treated with prednisone alone for the same duration. The values of 24-h urinary protein excretion were 1.25+/-0.64 vs 2.52+/-0.56 g/24 h (P<0.05), 1.16+/-0.45 vs 2.42+/-0.24 g/24 h (P<0.05), and 1.10+/-0.41 vs 2.05+/-0.46 g/24 h (P<0.05) in group I and group II patients, respectively, at 4, 8, and 12 weeks. Patients in group I showed lower serum concentrations of urinary retinol-binding protein and beta(2)-microglobulin (P<0.01) at the end of the study, but the patients' blood pressure and components of the renin-angiotensin system (RAS) had no change during treatment. The result suggested that fosinopril significantly reduced proteinuria and alleviated renal tubular damage, but did not influence blood pressure and components of systemic RAS in normotensive children with SRINS.

Familial hematurias: what we know and what we don't

Over the past 30 years we have learned a great deal about the molecular genetics and natural history of familial forms of hematuria. Our enhanced understanding of these conditions has yet to generate effective therapies for Alport syndrome, the form of familial hematuria associated with end-stage renal disease. This review briefly presents the current state of knowledge about familial hematuria and argues for the organization of clinical therapeutic trials in Alport syndrome.

Distinct time courses of renal protective action of angiotensin receptor antagonists and ACE inhibitors in chronic renal disease

Although the angiotensin receptor antagonist (ARB) shares the angiotensin-II-blocking activity with the angiotensin-converting enzyme inhibitor (ACE-I), pharmacological mechanisms of action of these agents differ. We evaluated the temporal profiles of action of ACE-I and ARB on urinary protein excretion and nitrate/nitrate (NO(x)) excretion in hypertensive (140 and/or 90 mmHg) patients with chronic renal disease (serum creatinine < 265 (range, 44-265) micromol/l or creatinine clearance > 30 (range, 30-121) ml/min). Patients with mild (<1 g/day; range, 0.4-1.0) and moderate proteinuria (>1 g/day; range, 1.1-6.9) were randomly assigned to ACE-I- and ARB-treated groups, and were treated with ACE-I (trandolapril or perindopril) or ARB(losartan or candesartan) for 48 weeks. In all groups, treatment with ACE-I or ARB decreased blood pressure to the same level, but had no effect on creatinine clearance. In patients with mild proteinuria, neither ACE-I nor ARB altered urinary protein excretion. In patients with moderate proteinuria, ACE-I caused 44 +/- 6% reduction in proteinuria (from 2.7 +/- 0.5 to 1.5 +/- 0.4 g/day, n = 14) at 12 weeks, and this beneficial effect persisted throughout the protocol (48 weeks, 1.2 +/- 0.2 g/day). In contrast, ARB did not produce a significant decrease in proteinuria at 12 weeks (23 +/- 8%, n = 13), but a 41 +/- 6% reduction in proteinuria was observed at 48 weeks. Similarly, although early (12 weeks) increases in urinary NO(x) excretion were observed with ACE-I (from 257 +/- 70 to 1111 +/- 160 micromol/day) and ARB (from 280 +/- 82 to 723 +/- 86 micromol/day), the ARB-induced increase in NO(x) excretion was smaller than that by ACE-I (P < 0.05). In conclusion, although both ACE-I and ARB reduce blood pressure similarly, the effect of these agents on proteinuria differs in chronic renal disease with moderate proteinuria. Relatively early onset of the proteinuria-reducing effect was observed with ACE-I, which paralleled the increase in urinary NO(x) excretion. Conversely, ARB decreased proteinuria and increased urinary NO(x) excretion gradually. These time course-dependent changes in proteinuria and urinary NO(x) may reflect the pharmacological property of ACE-I and ARB, with regard to the action on bradykinin.

Differing Anti-Proteinuric Action of Candesartan and Losartan in Chronic Renal Disease

It has becoming clear that angiotensin receptor blockers (ARBs) show varying levels of angiotensin II type 1 (AT1) receptor blocking activity. Although the duration of activity and the efficacy on blood pressure of ARB are reported to vary, depending on the agents used, it has not been examined whether the effects on proteinuria and urinary nitrite/nitrate (NOx) excretion differ in hypertensive patients with chronic renal disease. In the present study, patients with hypertension (> 140 and/or 90 mmHg) and chronic renal disease (proteinuria > 0.5g/day; serum creatinine < 265 micromol/l or creatinine clearance > 30 ml/min/1.72 m2) were randomly assigned to perindopril- (n = 15), trandolapril- (n = 15), candesartan- (n = 17), and losartan-treated groups (n = 15), and were followed up for 96 weeks. All agents decreased blood pressure to the same level, and none of them had any effect on creatinine clearance. Candesartan, perindopril, and trandolapril reduced proteinuria markedly (from 3.0 +/- 0.6 to 1.8 +/- 0.5 g/day, 2.7 +/- 0.5 to 1.6 +/- 0.4 g/day, and 2.7 +/- 0.5 to 1.7 +/- 0.4 g/day, respectively) at 12 weeks, and the beneficial effect persisted throughout the study. The effect of losartan, however, diminished over the study period. Whereas perindopril, trandolapril, and candesartan markedly increased urinary NOx excretion (from 257 +/- 23 to 1,011 +/- 150 micromol/day, 265 +/- 70 to 986 +/- 130 micromol/day, and 260 +/- 62 to 967 +/- 67 micromol/day at 12 weeks, respectively), a relatively blunted increase was observed with losartan (from 309 +/- 42 to 596 +/- 64 micromol/day). In conclusion, renal action of ARB varies, with relatively less proteinuria-sparing, as well as NOx-enhancing, effects observed with candesartan showing the greatest reduction of proteinuria and greatest enhancement of NOx. Furthermore, renal nitric oxide may contribute to the renal protective action of these agents when administered to patients with chronic renal disease.