Andrea Fekete

Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure

Antenatal Bartter syndrome (aBS) comprises a heterogeneous group of autosomal recessive salt-losing nephropathies. Identification of three genes that code for renal transporters and channels as responsible for aBS has resulted in new insights into renal salt handling, diuretic action and blood-pressure regulation. A gene locus of a fourth variant of aBS called BSND, which in contrast to the other forms is associated with sensorineural deafness (SND) and renal failure, has been mapped to chromosome 1p. We report here the identification by positional cloning, in a region not covered by the human genome sequencing projects, of a new gene, BSND, as the cause of BSND. We examined ten families with BSND and detected seven different mutations in BSND that probably result in loss of function. In accordance with the phenotype, BSND is expressed in the thin limb and the thick ascending limb of the loop of Henle in the kidney and in the dark cells of the inner ear. The gene encodes a hitherto unknown protein with two putative transmembrane α-helices and thus might function as a regulator for ion-transport proteins involved in aBS, or else as a new transporter or channel itself.

Reference Values of Pulse Wave Velocity in Healthy Children and Teenagers

Carotid-femoral pulse wave velocity is an established method for characterizing aortic stiffness, an individual predictor of cardiovascular mortality in adults. Normal pulse wave velocity values for the pediatric population derived from a large data collection have yet to be available. The aim of this study was to create a reference database and to characterize the factors determining pulse wave velocity in children and teenagers. Carotid-femoral pulse wave velocity was measured by applanation tonometry. Reference tables from pulse wave velocities obtained in 1008 healthy subjects (aged between 6 and 20 years; 495 males) were generated using a maximum-likelihood curve-fitting technique for calculating SD scores in accordance with the skewed distribution of the raw data. Effects of sex, age, height, weight, blood pressure, and heart rate on pulse wave velocity were assessed. Sex-specific reference tables and curves for age and height are presented. Pulse wave velocity correlated positively (P<0.001) with age, height, weight, and blood pressure while correlating negatively with heart rate. After multiple regression analysis, age, height, and blood pressure remained major predictors of pulse wave velocity. This study, involving >1000 children, is the first to provide reference values for pulse wave velocity in children and teenagers, thereby constituting a suitable tool for longitudinal clinical studies assessing subgroups of children who are at long-term risk of cardiovascular disease.

Heat shock protein 72 (HSPA1B) gene polymorphism and Toll-like receptor (TLR) 4 mutation are associated with increased risk of urinary tract infection in children.

Innate immunity and urinary tract response play a central role in the development of urinary tract infection (UTI). Heat shock protein (HSP) 72 and Toll-like receptor (TLR) 4 are among the key elements of innate defence mechanisms. This study assesses the role of HSPA1B A(1267)G and TLR4 A(896)G polymorphisms using allele-specific polymerase chain reaction in 103 patients treated with recurrent UTI. Allelic prevalence was compared with reference values of 235 healthy controls. Clinical data were also statistically evaluated. TLR4 (896)AG genotype and TLR4 (896)G allele had also higher prevalence in UTI patients versus controls (p = 0.031 and 0.041, respectively). Our data indicates a relationship between the carrier status of HSPA1B (1267)G and TLR4 (896)G alleles and the development of recurrent UTI in childhood independently of other renal abnormalities, while raising further questions about the clinical and therapeutic relevance of these polymorphisms in everyday pediatric nephrology.

Phosphorylation by casein kinase 2 induces PACS-1 binding of nephrocystin and targeting to cilia

Mutations in proteins localized to cilia and basal bodies have been implicated in a growing number of human diseases. Access of these proteins to the ciliary compartment requires targeting to the base of the cilia. However, the mechanisms involved in transport of cilia proteins to this transitional zone are elusive. Here we show that nephrocystin, a ciliary protein mutated in the most prevalent form of cystic kidney disease in childhood, is expressed in respiratory epithelial cells and accumulates at the base of cilia, overlapping with markers of the basal body area and the transition zone. Nephrocystin interacts with the phosphofurin acidic cluster sorting protein (PACS)‐1. Casein kinase 2 (CK2)‐mediated phosphorylation of three critical serine residues within a cluster of acidic amino acids in nephrocystin mediates PACS‐1 binding, and is essential for colocalization of nephrocystin with PACS‐1 at the base of cilia. Inhibition of CK2 activity abrogates this interaction and results in the loss of correct nephrocystin targeting. These data suggest that CK2‐dependent transport processes represent a novel pathway of targeting proteins to the cilia.

Anti-Citrullinated Protein Antibodies in Rheumatoid Arthritis: As Good as it Gets?

Anti-citrullinated protein antibodies (ACPAs) have recently emerged as sensitive and specific serological markers of rheumatoid arthritis (RA), providing superior alternative of the rheumatoid factor (RF) test in the laboratory diagnostics of RA. The first members of this autoantibody family were anti-perinuclear factor (APF) and anti-keratin antibodies (AKA). It became evident that both APF and AKA recognize citrullinated epitopes of filaggrin. Citrullination is a post-translational modification of arginine by deimination, physiologically occurring during apoptosis, inflammation or keratinization. The presence of several citrullinated proteins has been demonstrated in the RA synovium. The identification of citrullinated epitopes as targets for anti-filaggrin antibodies led to the development of the first and later second generation anti-cyclic citrullinated peptide (anti-CCP) antibody assays. The widely used anti-CCP2 assays have high diagnostic sensitivity and specificity, and they also show important predictive and prognostic value in RA. The anti-Sa antibody has been identified a decade ago; however, recent studies confirmed that anti-Sa is directed against citrullinated vimentin, hence it is a new member of the family of ACPAs. The newly developed anti-mutated citrullinated vimentin (anti-MCV) assay has similar diagnostic performance than the anti-CCP2 ELISA; however, the diagnostic spectrum of the anti-MCV test is somewhat different from that of anti-CCP2. It’s especially useful in the diagnosis of RA in RF and anti-CCP2 seronegative patients. The combined application of anti-CCP2 and anti-MCV assays can improve the laboratory diagnostics of RA. The family of ACPAs is expected to expand; there is an increasing need for developing new diagnostic strategies after careful evaluation of the characteristics of the available assays.

Fibrosis Related Inflammatory Mediators: Role of the IL-10 Cytokine Family

Importance of chronic fibroproliferative diseases (FDs) including pulmonary fibrosis, chronic kidney diseases, inflammatory bowel disease, and cardiovascular or liver fibrosis is rapidly increasing and they have become a major public health problem. According to some estimates about 45% of all deaths are attributed to FDs in the developed world. Independently of their etiology the common hallmark of FDs is chronic inflammation. Infiltrating immune cells, endothelial, epithelial, and other resident cells of the injured organ release an orchestra of inflammatory mediators, which stimulate the proliferation and excessive extracellular matrix (ECM) production of myofibroblasts, the effector cells of organ fibrosis. Abnormal amount of ECM disturbs the original organ architecture leading to the decline of function. Although our knowledge is rapidly expanding, we still have neither a diagnostic tool to detect nor a drug to specifically target fibrosis. Therefore, there is an urgent need for the more comprehensive understanding of the pathomechanism of fibrosis and development of novel diagnostic and therapeutic strategies. In the present review we provide an overview of the common key mediators of organ fibrosis highlighting the role of interleukin-10 (IL-10) cytokine family members (IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26), which recently came into focus as tissue remodeling-related inflammatory cytokines.

Association between Estrogen Receptor α (ESR1) Gene Polymorphisms and Severe Preeclampsia

Associations have been reported between estrogen receptor α (ESR1) gene polymorphisms and various pathological conditions, including cardiovascular diseases. Our aim was to investigate whether two polymorphisms of the ESR1 gene (ESR1 c.454 −397T>C: PvuII restriction site and c.454 −351A>G: XbaI restriction site) are associated with preeclampsia. In a case-control study, we analyzed blood samples from 119 severely preeclamptic patients and 103 normotensive, healthy pregnant women using the polymerase chain reaction (PCR)−restriction fragment length polymorphism (RFLP) method. All of the women were Caucasian. There was no association between severe preeclampsia and the PvuII and XbaI ESR1 gene polymorphisms separately. However, with the simultaneous carriage of both polymorphisms, the TT/AA genotype combination was significantly more frequent in severely preeclamptic patients than in healthy control subjects (24.4% vs. 9.7%, p=0.003), whereas the TT/AG combination was significantly less frequent in the severely preeclamptic group than in the control group (5.0% vs. 18.4%, p=0.002). According to the haplotype estimation, the homozygous T-A haplotype carriers had an increased risk of severe preeclampsia independent of maternal age, prepregnancy BMI, primiparity and smoking status (adjusted odds ratio [OR]: 4.36, 95% confidence interval [CI]: 1.65–11.53). The GG genotype of the XbaI polymorphism was associated with a lower risk of fetal growth restriction in patients with severe preeclampsia (OR: 0.23, 95% CI: 0.07–0.73). In conclusion, the homozygous T-A haplotype carriers of ESR1 PvuII and XbaI polymorphisms showed an increased risk of severe preeclampsia. In addition, the GG genotype of the XbaI polymorphism decreased the risk of fetal growth restriction in severely preeclamptic patients.

Pulse Wave Velocity in End-Stage Renal Disease: Influence of Age and Body Dimensions

Arterial stiffness increases with age. This process is accelerated by end-stage renal disease (ESRD). Pulse wave velocity (PWV) increases with arterial stiffness. In this study, PWV of 133 healthy individuals (6–23 y of age) and 11 patients on dialysis was measured to establish the normal values of PWV and to compare them with those in ESRD. Age-matched (A-C) and height- and weight-matched (H/W-C) control groups were used. Thereafter, PWV was indexed to height and the data were reevaluated. The role of the risk factors including serum calcium, phosphate, parathyroid hormone (PTH), and the time on dialysis was analyzed using a score system. PWV correlated with age, weight, height, blood pressure, and heart rate. ESRD patients were smaller than A-C and older than H/W-C. PWV of patients with ESRD did not differ from A-C; however, it was elevated in comparison to H/W-C. In both healthy and ESRD patients, the PWV/height ratio was independent of age. PWV/height was increased in ESRD. There was a correlation between PWV/height and the risk factor score. Controls matched for height and weight or PWV/height should be used in cases of growth failure. A number of risk factors responsible for increased arterial stiffness are present in ESRD.

Association between Heat Shock Protein 72 Gene Polymorphism and Acute Renal Failure in Premature Neonates

Heat shock protein (HSP)70 plays an important role in the ischemic tolerance of fetal and neonatal kidney. We have investigated the association of genetic polymorphisms of the constitutive HSP70 (HSP73) and the inducible HSP70 (HSP72) encoding genes with the risk of acute renal failure (ARF) in very low birth weight (VLBW) neonates. Thirty-seven VLBW neonates with ARF and 93 VLBW neonates without ARF were enrolled in the study. The presence of HSP72 (1267)AG and HSP73 (190)GC polymorphism was analyzed from dried blood samples by PCR and restriction length fragment polymorphism. Allelic prevalence was related to reference values obtained in 131 healthy adults. Stepwise binary logistic regression was applied to determine the independent effect of the established risk factors to the development of ARF. Sixteen of 37 VLBW neonates with ARF and 18 of 93 VLBW neonates without ARF were homozygous for HSP72 (1267)G allele (p ≤ 0.01). The association between HSP72 (1267)GG genotype and ARF remained at the level of significance (p = 0.05) when it was adjusted for established risk factors of neonatal ARF. Prevalence of HSP72 (1267)GG was also higher in VLBW neonates than in the reference population (p < 0.05) and in VLBW neonates with infant respiratory distress syndrome than in those without (p < 0.001). We found that in VLBW neonates carrying HSP72 (1267)GG genetic variation, which is associated with low inducibility of HSP72, the risk of ARF was increased. Therefore, VLBW neonates with (1267)GG might express less HSP72 and might be less protected against ARF.

Sex differences in the alterations of Na+,K+‐ATPase following ischaemia–reperfusion injury in the rat kidney

Postischaemic acute renal failure (ARF) is influenced by sex. Na+,K+‐ATPase (NKA) plays a crucial role in the pathogenesis of postischaemic ARF. We tested the impact of sex on mRNA, protein expression, cellular distribution and enzyme activity of NKA following renal ischaemia–reperfusion (I‐R) injury. The left renal pedicle of uninephrectomized female (F) and male (M) Wistar rats was clamped for 55 min followed by 2 h (T2) and 16 h (T16) of reperfusion. Uninephrectomized, sham‐operated F and M rats served as controls (n= 6 per group). Blood urea nitrogen, serum creatinine and renal histology were evaluated to detect the severity of postischaemic ARF. mRNA expression of NKA α1 and β1 subunits were detected by RT‐PCR. The effect of I‐R on cellular distribution was compared by Triton X‐100 extraction. Cellular proteins were divided into Triton‐insoluble and Triton‐soluble fractions and assessed by Western blot. NKA enzyme activity was also determined. After the ischaemic insult blood urea nitrogen and serum creatinine were higher and renal histology showed more rapid progression in M versus  F (P < 0.05). mRNA expression of the NKA α1 subunit decreased in I‐R groups versus controls, but was higher in F versus M both in control and I‐R groups (P < 0.05). However, protein levels of the NKA α1 subunit in total tissue homogenate did not differ in controls, but were higher in F versus M in I‐R groups (P < 0.05). Triton X‐100 extractability was lower in F versus M at T16 (P < 0.05). NKA enzyme activity was the same in controls, but was higher in F versus M in I‐R groups (T2: 14.9 ± 2.3 versus 9.15 ± 2.21 U) (T16: 11.7 ± 4.1 versus 5.65 ± 2.3 U; P < 0.05). mRNA and protein expression of the NKA β1 subunit did not differ between F and M in any of the protocol. We concluded that NKA is more protected from the detrimental effects of postischaemic injury in females. Higher mRNA and protein expression of the NKA α1 subunit and higher enzyme activity might be additional contributing factors to the improved postischaemic renal function of female rats.