Mineralocorticoid effects in the kidney: correlation between alphaENaC, GILZ, and Sgk-1 mRNA expression and urinary excretion of Na+ and K+.

Aldosterone exerts its effects through interactions with two types of binding sites, the mineralocorticoid (MR) and the glucocorticoid (GR) receptors. Although both receptors are known to be involved in the anti-natriuretic response to aldosterone, the mechanisms of signal transduction leading to modulation of electrolyte transport are not yet fully understood. This study measured the Na(+) and K(+) urinary excretion and the mRNA levels of three known aldosterone-induced transcripts, the serum and glucocorticoid-induced kinase (Sgk-1), the alpha subunit of the epithelial Na(+) channel (alphaENaC), and the glucocorticoid-induced-leucine-zipper protein (GILZ) in the whole kidney and in isolated cortical collecting tubules of adrenalectomized rats treated with low doses of aldosterone and/or dexamethasone. The resulting plasma concentrations of both steroids were close to 1 nmol/L. Aldosterone, given with or without dexamethasone, induced anti-natriuresis and kaliuresis, whereas dexamethasone alone did not. GILZ and alphaENaC transcripts were higher after treatment with either or both hormones, whereas the mRNA abundance of Sgk-1 was increased in the cortical collecting tubule by aldosterone but not by dexamethasone. We conclude the increased expression of Sgk-1 in the cortical collecting tubules is a primary event in the early antinatriuretic and kaliuretic responses to physiologic concentrations of aldosterone. Induction of alphaENaC and/or GILZ mRNAs may play a permissive role in the enhancement of the early and/or late responses; these effects may be necessary for a full response but do not by themselves promote early changes in urinary Na(+) and K(+) excretion.

Two-kidney, one clip and one-kidney, one clip hypertension in mice.

The mouse remains the animal of choice in transgenic experiments, creating a need for methods of evaluating the physiology of genetically modified animals. We have established and characterized two murine models of renovascular hypertension known as the two-kidney, one clip and one-kidney, one clip models. The appropriate size of the clip lumen needed to induce high blood pressure was determined to be 0.12 mm. Clips with a lumen of 0.11 mm induced a high percentage of renal infarction, and clips with a 0.13-mm opening did not produce hypertension. Four weeks after clipping, two-kidney, one clip hypertensive mice exhibited blood pressure approximately 20 mm Hg higher than their sham-operated controls. After a similar period, this increase reached almost 35 mm Hg in the one-kidney, one clip model. Depending on the model, mice develop either renin-dependent or renin-independent hypertension. Both models are characterized by the development of cardiovascular hypertrophy.

Pretransplant pulmonary hypertension and long-term allograft right ventricular function.

Background: Graft right ventricular (RV) function is compromised directly posttransplant, especially in heart transplantation (HTx) recipients with pretransplant pulmonary hypertension (PH). Graft RV size and systolic function, and the effect of the recipient's pulmonary haemodynamics on the graft extracellular matrix are not well characterised in the patients long-term after HTx. Aim: Comparison of RV size and systolic function in HTx recipients' long-term posttransplant stratified by the presence of pretransplant PH. Methods: HTx survivors >/=2 years posttransplant were divided into group I without pretransplant PH (pulmonary vascular resistance, PVR <2.5Wood units, n=37) and group II with PH (PVR >/=2.5Wood units, n=16). RV size and systolic function were measured using cardiac magnetic resonance imaging (CMR). The collagen content was assessed in septal endomyocardial biopsies obtained at HTx and at study inclusion. Results: Mean posttransplant follow-up was 5.2+/-2.9 years (group I) and 4.9+/-2.2 years (group II) (p=0.70). PVR was 1.5+/-0.6 vs 4.1+/-1.7Wood units pretransplant (p<0.001), and 1.2+/-0.5 vs 1.3+/-0.5Wood units at study inclusion (p=0.43). Allograft RV size and systolic function were similar in both groups (p always >/=0.07). Collagen content at transplantation and at follow-up were not different (p always >/=0.60). Conclusion: Posttransplant normalisation of pretransplant PH is associated with normal graft RV function long-term after HTx.

A new technique with high reproducibility to estimate renal oxygenation using BOLD-MRI in chronic kidney disease.

OBJECTIVES: To assess inter-observer variability of renal blood oxygenation level-dependent MRI (BOLD-MRI) using a new method of analysis, called the concentric objects (CO) technique, in comparison with the classical ROI (region of interest)-based technique. METHODS: MR imaging (3T) was performed before and after furosemide in 10 chronic kidney disease (CKD) patients (mean eGFR 43±24ml/min/1.73m(2)) and 10 healthy volunteers (eGFR 101±28ml/min1.73m(2)), and R2* maps were determined on four coronal slices. In the CO-technique, R2* values were based on a semi-automatic procedure that divided each kidney in six equal layers, whereas in the ROI-technique, all circles (ROIs) were placed manually in the cortex and medulla. The mean R2*values as assessed by two independent investigators were compared. RESULTS: With the CO-technique, inter-observer variability was 0.7%-1.9% across all layers in non-CKD, versus 1.6%-3.8% in CKD. With the ROI-technique, median variability for cortical and medullary R2* values was 3.6 and 6.8% in non-CKD, versus 4.7 and 12.5% in CKD; similar results were observed after furosemide. CONCLUSION: The CO-technique offers a new, investigator-independent, highly reproducible alternative to the ROI-based technique to estimate renal tissue oxygenation in CKD.

Fibrose rétropéritonéale: cause rare d'insuffisance rénale postrénale, a ne pas méconnaître [Retroperitoneal fibrosis: a rare cause of postrenal kidney failure, no to be missed].

We report the observation of a fifty years old man, admitted in the emergency room for bilateral lumbar pain and hyperkaliemic metabolic acidosis, and postrenal kidney failure induced by bilateral hydronephrosis. Radiographic exploration and histologic studies of biopsy confirmed an idiopathic retroperitoneal fibrosis that clinically and biologicaly responded to three seances of hemodialysis, and insertion in each uretere of one double J stent, and long term corticotherapy. The retroperitoneal fibrosis is a little common inflammatory disease, characterized by the development of a fibrous mass around the retroperitoneal structures. His diagnostic means evolved. On the other hand, his treatment was the object of no checked controlled and randomized trial. This article proposes an updating of the knowledge on this subject.

Atrial arrhythmias in adult patients with right- versus left-sided congenital heart disease anomalies.

Atrial arrhythmias (AAs) are a common complication in adult patients with congenital heart disease. We sought to compare the lifetime prevalence of AAs in patients with right- versus left-sided congenital cardiac lesions and their effect on the prognosis. A congenital heart disease diagnosis was assigned using the International Disease Classification, Ninth Revision, diagnostic codes in the administrative databases of Quebec, from 1983 to 2005. Patients with AAs were those diagnosed with an International Disease Classification, Ninth Revision, code for atrial fibrillation or intra-atrial reentry tachycardia. To ensure that the diagnosis of AA was new, a washout period of 5 years after entry into the database was used, a period during which the patient could not have received an International Disease Classification, Ninth Revision, code for AA. The cumulative lifetime risk of AA was estimated using the Practical Incidence Estimators method. The hazard ratios (HRs) for mortality, morbidity, and cardiac interventions were compared between those with right- and left-sided lesions after adjustment for age, gender, disease severity, and cardiac risk factors. In a population of 71,467 patients, 7,756 adults developed AAs (isolated right-sided, 2,229; isolated left-sided, 1,725). The lifetime risk of developing AAs was significantly greater in patients with right- sided than in patients with left-sided lesions (61.0% vs 55.4%, p <0.001). The HR for mortality and the development of stroke or heart failure was similar in both groups (HR 0.96, 95% confidence interval [CI] 0.86 to 1.09; HR 0.94, 95% CI 0.80 to 1.09; and HR 1.10, 95% CI 0.98 to 1.23, respectively). However, the rates of cardiac catheterization (HR 0.63, 95% CI 0.55 to 0.72), cardiac surgery (HR 0.40, 95% CI 0.36 to 0.45), and arrhythmia surgery (HR 0.77, 95% CI 0.6 to 0.98) were significantly less for patients with right-sided lesions. In conclusion, patients with right-sided lesions had a greater lifetime burden of AAs. However, their morbidity and mortality were no less than those with left-sided lesions, although the rate of intervention was substantially different.

Anti-HLA antibody repertoire after IVIg infusion in highly sensitized patients waiting for kidney transplantation.

Polyclonal intravenous immunoglobulin (IVIg) treatment reduces crossmatch positivity and increases rates of transplantation in highly sensitised patients (HS). We quantified the panel reactive antibody (PRA) by microlymphocytotoxicity (MLCC), and we analysed anti-HLA class I and class II IgG specific antibody repertoire by Luminex before and after IVIg infusion alone in HS patients awaiting kidney transplantation. Five patients received three monthly infusions of 1 g/kg of IVIg. Serum samples collected pre and post IVIg treatment were submitted for PRA analysis by MLCC. Anti-class I and anti-class II antibody specificities were then tested by Luminex. We focused on the anti-HLA class I and class II antibodies directed against HLA expressed by a previous graft. We also analysed the anti-HLA antibody repertoire in three patients who had not received IVIg infusion. The PRA level determined by MLCC decreased significantly in one of the five patients, dropping from 40% to 17%. The Luminex assay showed fluctuations of the anti-HLA antibody levels over time, but no significant longterm modifications of the anti-HLA antibody repertoire were observed, even in the patient with a strong and prolonged reduction of the PRA determined by MLCC. Our results show that IVIg at 1 g/kg is not sufficient to reduce PRA and does not modify the repertoire of specific anti-HLA antibody determined by Luminex.

ERK1/2 controls Na,K-ATPase activity and transepithelial sodium transport in the principal cell of the cortical collecting duct of the mouse kidney.

The collecting duct of normal kidney exhibits significant activity of the MEK1/2-ERK1/2 pathway as shown in vivo by immunostaining of phosphorylated active ERK1/2 (pERK1/2). The MEK1/2-ERK1/2 pathway controls many different ion transports both in proximal and distal nephron, raising the question of whether this pathway is involved in the basal and/or hormone-dependent transepithelial sodium reabsorption in the principal cell of the cortical collecting duct (CCD), a process mediated by the apical epithelial sodium channel and the basolateral sodium pump (Na,K-ATPase). To answer this question we used ex vivo microdissected CCDs from normal mouse kidney or in vitro cultured mpkCCDcl4 principal cells. Significant basal levels of pERK1/2 were observed ex vivo and in vitro. Aldosterone and vasopressin, known to up-regulate sodium reabsorption in CCDs, did not change ERK1/2 activity either ex vivo or in vitro. Basal and aldosterone- or vasopressin-stimulated sodium transport was down-regulated by the MEK1/2 inhibitor PD98059, in parallel with a decrease in pERK1/2 in vitro. The activity of Na,K-ATPase but not that of epithelial sodium channel was inhibited by MEK1/2 inhibitors in both unstimulated and aldosterone- or vasopressin-stimulated CCDs in vitro. Cell surface biotinylation showed that intrinsic activity rather than cell surface expression of Na,K-ATPase was controlled by pERK1/2. PD98059 also significantly inhibited the activity of Na,K-ATPase ex vivo. Our data demonstrate that the ERK1/2 pathway controls Na,K-ATPase activity and transepithelial sodium transport in the principal cell and indicate that basal constitutive activity of the ERK1/2 pathway is a critical component of this control.

Overlap Between Common Genetic Polymorphisms Underpinning Kidney Traits and Cardiovascular Disease Phenotypes: The CKDGen Consortium.

BACKGROUND: Chronic kidney disease is associated with cardiovascular disease. We tested for evidence of a shared genetic basis to these traits. STUDY DESIGN: We conducted 2 targeted analyses. First, we examined whether known single-nucleotide polymorphisms (SNPs) underpinning kidney traits were associated with a series of vascular phenotypes. Additionally, we tested whether vascular SNPs were associated with markers of kidney damage. Significance was set to 1.5×10(-4) (0.05/325 tests). SETTING & PARTICIPANTS: Vascular outcomes were analyzed in participants from the AortaGen (20,634), CARDIoGRAM (86,995), CHARGE Eye (15,358), CHARGE IMT (31,181), ICBP (69,395), and NeuroCHARGE (12,385) consortia. Tests for kidney outcomes were conducted in up to 67,093 participants from the CKDGen consortium. PREDICTOR: We used 19 kidney SNPs and 64 vascular SNPs. OUTCOMES & MEASUREMENTS: Vascular outcomes tested were blood pressure, coronary artery disease, carotid intima-media thickness, pulse wave velocity, retinal venular caliber, and brain white matter lesions. Kidney outcomes were estimated glomerular filtration rate and albuminuria. RESULTS: In general, we found that kidney disease variants were not associated with vascular phenotypes (127 of 133 tests were nonsignificant). The one exception was rs653178 near SH2B3 (SH2B adaptor protein 3), which showed direction-consistent association with systolic (P = 9.3 ×10(-10)) and diastolic (P = 1.6 ×10(-14)) blood pressure and coronary artery disease (P = 2.2 ×10(-6)), all previously reported. Similarly, the 64 SNPs associated with vascular phenotypes were not associated with kidney phenotypes (187 of 192 tests were nonsignificant), with the exception of 2 high-correlated SNPs at the SH2B3 locus (P = 1.06 ×10(-07) and P = 7.05 ×10(-08)). LIMITATIONS: The combined effect size of the SNPs for kidney and vascular outcomes may be too low to detect shared genetic associations. CONCLUSIONS: Overall, although we confirmed one locus (SH2B3) as associated with both kidney and cardiovascular disease, our primary findings suggest that there is little overlap between kidney and cardiovascular disease risk variants in the overall population. The reciprocal risks of kidney and cardiovascular disease may not be genetically mediated, but rather a function of the disease milieu itself.

Being at the right place at the right time.

I am tremendously honored to receive the 2012 Women in Cell Biology Junior Award. In this essay, I recount my career path over the past 15 years. Although many details are specific to my own experiences, I hope that some generalizations can be made to encourage more women to pursue independent scientific careers. Mine is a story of choosing a captivating question, making the most of your opportunities, and finding a balance with life outside the lab.