Jean-Jacques Boffa

Angiotensin II Activates Collagen Type I Gene in the Renal Vasculature of Transgenic Mice During Inhibition of Nitric Oxide Synthesis Evidence for an Endothelin-Mediated Mechanism

BACKGROUNDnHypertension is frequently associated with renal vascular fibrosis. The purpose of this study was to investigate whether angiotensin II (Ang II) is involved in this fibrogenic process.nnnMETHODS AND RESULTSnExperiments were performed on transgenic mice harboring the luciferase gene under the control of the collagen I-alpha(2) chain promoter [procolalpha(2)(I)]. Hypertension was induced by chronic inhibition of NO synthesis (N(G)-nitro-L-arginine methyl ester, L-NAME). Procolalpha(2)(I) activity started to increase in the renal vasculature after 4 weeks of L-NAME treatment (P<0.01) and at 14 weeks reached 3- and 8-fold increases over control in afferent arterioles and glomeruli, respectively (P<0.001). Losartan, an AT(1) receptor antagonist, given simultaneously with L-NAME prevented the increase of procolalpha(2)(I) levels and attenuated the development of renal vascular fibrosis without normalizing systolic pressure increase. Because we found previously that endothelin mediated renal vascular fibrosis in the L-NAME model, the interaction between Ang II, endothelin, and procolalpha(2)(I) was investigated in ex vivo and short-term in vivo experiments. In both conditions, the Ang II-induced activation of procolalpha(2)(I) in renal cortex was blocked by an endothelin receptor antagonist.nnnCONCLUSIONSnDuring chronic inhibition of NO, the collagen I gene becomes activated, leading to the development of renal vascular fibrosis. Ang II is a major player in this fibrogenic process, and its effect on collagen I gene is independent of systemic hemodynamics and is at least partly mediated by the profibrogenic action of endothelin.

GFR Estimation Using the Cockcroft-Gault, MDRD Study, and CKD-EPI Equations in the Elderly

RESEARCH LETTER GFR Estimation Using the Cockcroft-Gault, MDRD Study, and CKD-EPI Equations in the Elderly To the Editor: Kidney function loss in the elderly results from physiologic aging of the kidney and lifelong pathologic insults; this translates into a high incidence of chronic kidney disease (CKD) and susceptibility to ischemic or toxic renal insults. Determining glomerular filtration rate (GFR) is necessary for diagnosing and classifying CKD and adjusting drug dosage. The Cockcroft-Gault (CG), 4-variable Modification of Diet in Renal Disease (MDRD) Study, and CKD Epidemiology Collaboration (CKD-EPI) equations are the most widely used GFR estimates. They incorporate serum creatinine (SCr) concentration with determinants of its muscular production, including age. Many studies have shown that GFR estimates gave very different results in the elderly, raising concerns about which equation should be used in this population, especially for therapeutic adaptation. The proportion of very old patients in the populations that were used to establish the estimation formulas is very low, especially for the CG equation. Thus, the validity of GFR estimates in the elderly remains a matter of debate. We evaluated and compared performances of the CG, MDRD Study, and CKD-EPI equations in a large cohort of old patients with CKD. Between January 2007 and September 2010, data from all patients 65 years and older referred for GFR measurement to Bichat and Tenon hospitals (Paris, France) were collected. Patients gave their consent for scientific use of anonymous data. Urinary clearance of Cr-EDTA was determined on 6 consecutive 30-

Progression and regression in renal vascular and glomerular fibrosis

End‐stage renal disease (ESRD) is characterized by the development of fibrotic lesions in the glomerular, interstitial and vascular compartments. Renal fibrogenesis, a common complication of diabetes and hypertension, is a complex dynamic process involving several players such as inflammatory agents, cytokines, vasoactive agents and enzymes participating in extracellular matrix assembly, anchoring or degradation. The only available treatment today against chronic renal failure is dialysis or kidney transplantation, making thus ESRD one of the most expensive diseases to treat on a per‐patient basis. An emerging challenge for clinicians, maybe the nephrologists Holy Grail in the 21st century, is to stop definitively the decline of renal function and, if possible, to achieve regression of renal fibrosis and restoration of renal structure. Over the last 5 years, different approaches have been tested in experimental models of nephropathy with variable degree of success. In this review, we will focus on the mechanisms of the hypertension‐associated fibrosis and the few recent studies that gave promising results for a therapeutic intervention.

Timing and Determinants of Erythropoietin Deficiency in Chronic Kidney Disease

BACKGROUND AND OBJECTIVESnAnemia in patients with CKD is highly related to impaired erythropoietin (EPO) response, the timing and determinants of which remain unknown.nnnDESIGN, SETTING, PARTICIPANTS, & MEASUREMENTSnThis study measured EPO levels and studied their relation to GFR measured by 51Cr-EDTA renal clearance (mGFR) in 336 all-stage CKD patients not receiving any erythropoiesis-stimulating agent.nnnRESULTSnIn patients with anemia defined by World Health Organization criteria (hemoglobin [Hb] <13 g/dl in men and 12 g/dl in women), EPO response to Hb level varied by mGFR level. EPO and Hb levels were negatively correlated (r=-0.22, P=0.04) when mGFR was >30 ml/min per 1.73 m(2), whereas they were not correlated when mGFR was <30 (r=0.09, P=0.3; P for interaction=0.01). In patients with anemia, the ratio of observed EPO to the level predicted by the equation for their Hb level decreased from 0.72 (interquartile range, 0.57-0.95) for mGFR ≥60 ml/min per 1.73 m(2) to 0.36 (interquartile range, 0.16-0.69) for mGFR <15. Obesity, diabetes with nephropathy other than diabetic glomerulopathy, absolute iron deficiency, and high C-reactive protein concentrations were associated with increased EPO levels, independent of Hb and mGFR.nnnCONCLUSIONSnAnemia in CKD is marked by an early relative EPO deficiency, but several factors besides Hb may persistently stimulate EPO synthesis. Although EPO deficiency is likely the main determinant of anemia in patients with advanced CKD, the presence of anemia in those with mGFR >30 ml/min per 1.73 m(2) calls for other explanatory factors.

Renal Effects of Omapatrilat and Captopril in Salt-Loaded, Nitric Oxide-Deficient Rats

Abstract—Inhibition of nitric oxide synthases causes systemic hypertension and renal injury in rats. Our objective was to examine whether omapatrilat, a vasopeptidase inhibitor that inhibits both angiotensin-converting enzyme (ACE) and neutral endopeptidase, could induce better regression of renal injury than ACE inhibitor alone. Ten groups of rats were studied. They were fed either a normal (0.8% NaCl) or a high (4% NaCl) sodium diet. Eight of these groups received NG-nitro-l-arginine methyl ester (l-NAME, 20 mg · kg−1 · d−1) in their drinking water. After 4 weeks, 1 group on each diet was killed and considered the l-NAME group, whereas the others received l-NAME alone, captopril (200 mg · kg−1 · d−1) plus l-NAME, or omapatrilat (80 mg · kg−1 · d−1) plus l-NAME for 4 additional weeks. In rats receiving l-NAME alone for 8 weeks, the mortality rate was ≈90%, irrespective of the diet. In contrast, all rats survived in the captopril and the omapatrilat groups. In rats fed a normal-sodium diet, captopril and omapatrilat normalized systolic blood pressure and induced a complete regression of renal injury. Creatinine clearance and proteinuria were also normalized. In the high-sodium-diet groups, both treatments were less efficient: blood pressure remained elevated, and the regression of renal fibrosis was only partial. Although proteinuria decreased significantly with captopril or omapatrilat, creatinine clearance remained lower than in the controls. These results demonstrate that, in nitric oxide–deficient rats fed a normal-sodium diet, ACE and vasopeptidase inhibitors exhibit a marked renoprotective effect, whereas these treatments are less efficient in rats fed a high-sodium diet.

Renal Function Can Improve at Any Stage of Chronic Kidney Disease

Introduction Even though renal function decline is considered relentless in chronic kidney disease (CKD), improvement has been shown in patients with hypertensive nephropathy. Whether this can occur in any type of nephropathy and at any stage is unknown as are the features of patients who improve. Methods We identified 406 patients in the NephroTest cohort with glomerular filtration rates (mGFR) measured by 51Cr-EDTA clearance at least 3 times during at least 2 years of follow-up. Individual examination of mGFR trajectories by 4 independent nephrologists classified patients as improvers, defined as those showing a sustained mGFR increase, or nonimprovers. Twelve patients with erratic trajectories were excluded. Baseline data were compared between improvers and nonimprovers, as was the number of recommended therapeutic targets achieved over time (specifically, for systolic and diastolic blood pressure, proteinuria, and use of renin angiotensin system blockers). Results Measured GFR improved over time in 62 patients (15.3%). Their median mGFR slope was +1.88[IQR 1.38, 3.55] ml/min/year; it was −2.23[−3.9, −0.91] for the 332 nonimprovers. Improvers had various nephropathies, but not diabetic glomerulopathy or polycystic kidney disease. They did not differ from nonimprovers for age, sex, cardiovascular history, or CKD stage, but their urinary albumin excretion rate was lower. Improvers achieved significantly more recommended therapeutic targets (2.74±0.87) than nonimprovers (2.44±0.80, p<0.01). They also had fewer CKD-related metabolic complications and a lower prevalence of 25OH-vitamin-D deficiency. Conclusion GFR improvement is possible in CKD patients at any CKD stage through stage 4–5. It is noteworthy that this GFR improvement is associated with a decrease in the number of metabolic complications over time.

Decrease in Urinary Creatinine Excretion in Early Stage Chronic Kidney Disease

Background Little is known about muscle mass loss in early stage chronic kidney disease (CKD). We used 24-hour urinary creatinine excretion rate to assess determinants of muscle mass and its evolution with kidney function decline. We also described the range of urinary creatinine concentration in this population. Methods We included 1072 men and 537 women with non-dialysis CKD stages 1 to 5, all of them with repeated measurements of glomerular filtration rate (mGFR) by 51Cr-EDTA renal clearance and several nutritional markers. In those with stage 1 to 4 at baseline, we used a mixed model to study factors associated with urinary creatinine excretion rate and its change over time. Results Baseline mean urinary creatinine excretion decreased from 15.3±3.1 to 12.1±3.3 mmol/24 h (0.20±0.03 to 0.15±0.04 mmol/kg/24 h) in men, with mGFR falling from ≥60 to <15 mL/min/1.73 m2, and from 9.6±1.9 to 7.6±2.5 (0.16±0.03 to 0.12±0.03) in women. In addition to mGFR, an older age, diabetes, and lower levels of body mass index, proteinuria, and protein intake assessed by urinary urea were associated with lower mean urinary creatinine excretion at baseline. Mean annual decline in mGFR was 1.53±0.12 mL/min/1.73 m2 per year and that of urinary creatinine excretion rate, 0.28±0.02 mmol/24 h per year. Patients with fast annual decline in mGFR of 5 mL/min/1.73 m2 had a decrease in urinary creatinine excretion more than twice as big as in those with stable mGFR, independent of changes in urinary urea as well as of other determinants of low muscle mass. Conclusions Decrease in 24-hour urinary creatinine excretion rate may appear early in CKD patients, and is greater the more mGFR declines independent of lowering protein intake assessed by 24-hour urinary urea. Normalizing urine analytes for creatininuria may overestimate their concentration in patients with reduced kidney function and low muscle mass.

Nephroangiosclerosis in Cerebral Autosomal Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy: Is NOTCH3 Mutation the Common Culprit?

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a systemic arterial disease characterized by impairment of vascular smooth muscle cell structure and function related to NOTCH3 mutations. Pathological findings include pathognomonic granular osmiophilic material (GOM) deposition with nonspecific hyalinization within the artery wall in a variety of tissues. The main clinical presentation is iterative strokes in young adults despite the lack of cardiovascular risk factors, leading to early dementia. Although arteriosclerosis and GOM have been found in kidneys from patients with CADASIL, kidney disease has been described only once up to now, in association with immunoglobulin A nephropathy. We report the case of a 61-year-old patient with a medical history of CADASIL and recent mild hypertension. His mother also showed neuropsychiatric symptoms and end-stage renal disease of unknown cause. The patient had a chronic kidney disease defined by means of estimated glomerular filtration rate using the 4-variable Modification of Diet in Renal Disease Study equation of 58 mL/min/1.73 m(2) associated with mild proteinuria and intermittent microscopic hematuria. Renal histological analysis showed severe arteriosclerosis and mild interstitial fibrosis. Glomeruli did not show mesangial immunoglobulin A deposition or focal segmental proliferation. Electron microscopic analysis showed typical GOM deposition in the vicinity of altered vascular smooth muscle cells in interlobular and juxtaglomerular arteries. The nephroangiosclerosis-like lesions were unusually severe in contrast to the recent mild hypertension. The presence of GOM strongly suggests that renal lesions were related to the NOTCH3 mutation. Here, we describe the first case of familial occurrence of kidney disease with decreased kidney function in the absence of coexisting nephropathy in patients with CADASIL. We discuss the role of NOTCH3 mutation in the pathogenesis of nephroangiosclerosis through functional impairment of renal microcirculation or primary Notch3-related vascular disease.

Reduced NOV/CCN3 Expression Limits Inflammation and Interstitial Renal Fibrosis after Obstructive Nephropathy in Mice.

The main hallmark of chronic kidney disease (CKD) is excessive inflammation leading to interstitial tissue fibrosis. It has been recently reported that NOV/CCN3 could be involved in kidney damage but its role in the progression of nephropathies is poorly known. NOV/CCN3 is a secreted multifunctional protein belonging to the CCN family involved in different physiological and pathological processes such as angiogenesis, inflammation and cancers. The purpose of our study was to determine the role of NOV/CCN3 in renal inflammation and fibrosis related to primitive tubulointerstitial injury. After unilateral ureteral obstruction (UUO), renal histology and real-time PCR were performed in NOV/CCN3-/- and wild type mice. NOV/CCN3 mRNA expression was increased in the obstructed kidneys in the early stages of the obstructive nephropathy. Interestingly, plasmatic levels of NOV/CCN3 were strongly induced after 7 days of UUO and the injection of recombinant NOV/CCN3 protein in healthy mice significantly increased CCL2 mRNA levels. Furthermore, after 7 days of UUO NOV/CCN3-/- mice displayed reduced proinflammatory cytokines and adhesion markers expression leading to restricted accumulation of interstitial monocytes, in comparison with their wild type littermates. Consequently, in NOV/CCN3-/- mice interstitial renal fibrosis was blunted after 15 days of UUO. In agreement with our experimental data, NOV/CCN3 expression was highly increased in biopsies of patients with tubulointerstitial nephritis. Thus, the inhibition of NOV/CCN3 may represent a novel target for the progression of renal diseases.

Association of a Low-Protein Diet With Slower Progression of CKD

Introduction Reducing protein intake is recommended for slowing chronic kidney disease (CKD) progression, but assessment of its true effectiveness is sparse. Methods Using the Maroni formula, we assessed dietary protein intake (DPI) from 24-hour urinary urea excretion in 1594 patients (67% men and 33% women) with CKD, 784 of whom also had 7-day food records. Cause-specific hazard ratios (HRs) and 95% confidence intervals for the competing risks of DPI-associated end-stage renal disease (ESRD) or death were estimated in 1412 patients with baseline glomerular filtration rate ≥15 ml/min per 1.73 m2, measured by 51Cr-EDTA renal clearance (mGFR). Results Overall, mean DPI estimated from urea excretion was 1.09 ± 0.30 g/kg of body weight per day (range = 0.34−2.76); 20% of patients had values > 1.3 g/kg per day, and 1.9% had values < 0.6 g/kg per day. Urea excretion and food records produced similar estimates of mean DPI. The lower the mGFR, the lower the mean DPI. Over a median follow-up of 5.6 years, there were 319 ESRD events and 189 pre-ESRD deaths. After adjusting for relevant covariates, each 0.1 g/kg daily higher baseline urea excretion−based DPI or food record−based DPI was associated with an HR for ESRD of 1.05 (95% confidence interval 1.01−1.10) or 1.09 (95% confidence interval 1.04−1.14), respectively. HRs were stronger in patients with baseline mGFR < 30 ml/min per 1.73 m2. There was no association with mortality. The mean age of the patients was 59 ± 15 years, and mean body mass index was 26.6 ± 5.2 kg/m2. Conclusion In this prospective observational study, the lower the baseline DPI, the slower the progression toward ESRD. Most importantly, the absence of threshold for the relation between DPI and ESRD risk indicates that there is no optimal DPI in the range observed in this cohort.