Nora F. Banki

Recessive HYDIN mutations cause primary ciliary dyskinesia without randomization of left-right body asymmetry.

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous recessive disorder characterized by defective cilia and flagella motility. Chronic destructive-airway disease is caused by abnormal respiratory-tract mucociliary clearance. Abnormal propulsion of sperm flagella contributes to male infertility. Genetic defects in most individuals affected by PCD cause randomization of left-right body asymmetry; approximately half show situs inversus or situs ambiguous. Almost 70 years after the hy3 mouse possessing Hydin mutations was described as a recessive hydrocephalus model, we report HYDIN mutations in PCD-affected persons without hydrocephalus. By homozygosity mapping, we identified a PCD-associated locus, chromosomal region 16q21-q23, which contains HYDIN. However, a nearly identical 360 kb paralogous segment (HYDIN2) in chromosomal region 1q21.1 complicated mutational analysis. In three affected German siblings linked to HYDIN, we identified homozygous c.3985G>T mutations that affect an evolutionary conserved splice acceptor site and that subsequently cause aberrantly spliced transcripts predicting premature protein termination in respiratory cells. Parallel whole-exome sequencing identified a homozygous nonsense HYDIN mutation, c.922A>T (p.Lys307(∗)), in six individuals from three Faroe Island PCD-affected families that all carried an 8.8 Mb shared haplotype across HYDIN, indicating an ancestral founder mutation in this isolated population. We demonstrate by electron microscopy tomography that, consistent with the effects of loss-of-function mutations, HYDIN mutant respiratory cilia lack the C2b projection of the central pair (CP) apparatus; similar findings were reported in Hydin-deficient Chlamydomonas and mice. High-speed videomicroscopy demonstrated markedly reduced beating amplitudes of respiratory cilia and stiff sperm flagella. Like the hy3 mouse model, all nine PCD-affected persons had normal body composition because nodal cilia function is apparently not dependent on the function of the CP apparatus.

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.

The importance of different immunosuppressive regimens in the development of posttransplant diabetes mellitus

Prokai A, Fekete A, Pasti K, Rusai K, Banki NF, Reusz G, Szabo AJ. The importance of different immunosuppressive regimens in the development of posttransplant diabetes mellitus.

Decreased mucosal expression of intestinal alkaline phosphatase in children with coeliac disease

A major function of the enzyme intestinal alkaline phosphatase (iAP) is the detoxification of lipopolysaccharide (LPS), the ligand of Toll-like receptor 4 (TLR4). Hence, iAP has a role in the defence of maintaining intestinal barrier integrity. As intestinal barrier integrity is impaired in coeliac disease (CD), we tested the expression and localization of iAP in duodenal mucosa specimens from children with newly diagnosed CD (n = 10), with CD on gluten-free diet (GFD) (n = 5) and compared to those from ten healthy children. The mRNA and protein expression was determined by RT-PCR and Western blot analysis, respectively. Tissue localization of iAP and TLR4 was determined by immunofluorescence staining. iAP protein expression level was significantly lower than normal in newly diagnosed CD, while it was normalised in children on GFD. iAP and TLR4 colocalized at the epithelial surface of duodenal mucosa in each group of subjects enrolled. The finding of decreased iAP protein levels in newly diagnosed CD is consistent with its role in decreased intestinal barrier integrity. The latter may be the result of decreased LPS-detoxifying ability.

Aldosterone antagonists in monotherapy are protective against streptozotocin-induced diabetic nephropathy in rats

Angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARB) are the standard clinical therapy of diabetic nephropathy (DN), while aldosterone antagonists are only used as adjuncts. Previously in experimental DN we showed that Na/K ATPase (NKA) is mislocated and angiotensin II leads to superimposed renal progression. Here we investigated the monotherapeutic effect of aldosterone blockers on the progression of DN and renal NKA alteration in comparison to ACEi and ARBs. Streptozotocin-diabetic rats developing DN were treated with aldosterone antagonists; ACEi and ARB. Renal function, morphology, protein level and tubular localization of NKA were analyzed. To evaluate the effect of high glucose per se; HK-2 proximal tubular cells were cultured in normal or high concentration of glucose and treated with the same agents. Aldosterone antagonists were the most effective in ameliorating functional and structural kidney damage and they normalized diabetes induced bradycardia and weight loss. Aldosterone blockers also prevented hyperglycemia and diabetes induced increase in NKA protein level and enzyme mislocation. A monotherapy with aldosterone antagonists might be as, or more effective than ACEi or ARBs in the prevention of STZ-induced DN. Furthermore the alteration of the NKA could represent a novel pathophysiological feature of DN and might serve as an additional target of aldosterone blockers.

σ1-Receptor Agonism Protects against Renal Ischemia-Reperfusion Injury

Mechanisms of renal ischemia-reperfusion injury remain unresolved, and effective therapies are lacking. We previously showed that dehydroepiandrosterone protects against renal ischemia-reperfusion injury in male rats. Here, we investigated the potential role of σ1-receptor activation in mediating this protection. In rats, pretreatment with either dehydroepiandrosterone or fluvoxamine, a high-affinity σ1-receptor agonist, improved survival, renal function and structure, and the inflammatory response after sublethal renal ischemia-reperfusion injury. In human proximal tubular epithelial cells, stimulation by fluvoxamine or oxidative stress caused the σ1-receptor to translocate from the endoplasmic reticulum to the cytosol and nucleus. Fluvoxamine stimulation in these cells also activated nitric oxide production that was blocked by σ1-receptor knockdown or Akt inhibition. Similarly, in the postischemic rat kidney, σ1-receptor activation by fluvoxamine triggered the Akt-nitric oxide synthase signaling pathway, resulting in time- and isoform-specific endothelial and neuronal nitric oxide synthase activation and nitric oxide production. Concurrently, intravital two-photon imaging revealed prompt peritubular vasodilation after fluvoxamine treatment, which was blocked by the σ1-receptor antagonist or various nitric oxide synthase blockers. In conclusion, in this rat model of ischemia-reperfusion injury, σ1-receptor agonists improved postischemic survival and renal function via activation of Akt-mediated nitric oxide signaling in the kidney. Thus, σ1-receptor activation might provide a therapeutic option for renoprotective therapy.

Role of O-linked N-acetylglucosamine modification in diabetic nephropathy

Increased O-linked β-N-acetylglucosamine glycosylation (O-GlcNAcylation) is a known contributor to diabetes; however, its relevance in diabetic nephropathy (DN) is poorly elucidated. Here, we studied the process and enzymes of O-GlcNAcylation with a special emphasis on Akt-endothelial nitric oxide synthase (eNOS) and heat shock protein (HSP)72 signaling. Since tubular injury is the prominent site of DN, the effect of hyperglycemia was first measured in proximal tubular (HK2) cells cultured in high glucose. In vivo O-GlcNAcylation and protein levels of O-GlcNAc transferase (OGT), O-GlcNAcase (OGA), phosphorylated (p)Akt/Akt, peNOS/eNOS, and HSP72 were assessed in the kidney cortex of streptozotocin-induced diabetic rats. The effects of various renin-angiotensin-aldosterone system (RAAS) inhibitors were also evaluated. In proximal tubular cells, hyperglycemia-induced OGT expression led to increased O-GlcNAcylation, which was followed by a compensatory increase of OGA. In parallel, peNOS and pAkt levels decreased, whereas HSP72 increased. In diabetic rats, elevated O-GlcNAcylation was accompanied by decreased OGT and OGA. RAAS inhibitors ameliorated diabetes-induced kidney damage and prevented the elevation of O-GlcNAcylation and the decrement of pAkt, peNOS, and HSP72. In conclusion, hyperglycemia-induced elevation of O-GlcNAcylation contributes to the progression of DN via inhibition of Akt/eNOS phosphorylation and HSP72 induction. RAAS blockers successfully inhibit this process, suggesting a novel pathomechanism of their renoprotective action in the treatment of DN.

Heat Shock Protein Polymorphism Predisposes to Urinary Tract Malformations and Renal Transplantation in Children

BACKGROUND Anatomical malformations of the kidney and urinary tract account for 17% of pediatric renal transplantation procedures. Heat shock proteins (HSPs) are molecular chaperones with a protective function that promotes cell survival. HSP72 is an endogenous ligand for toll-like receptor TLR4, thereby stimulating innate immunity. Both in adults and children, decreased expression of HSP70s is associated with a number of kidney diseases. OBJECTIVE To assess the prevalence of HSPA1A G(190)C, HSPA1B A(1267)G, and TLR4 A(896)G polymorphisms in children who had undergone kidney transplantation. PATIENTS AND METHODS Genotypes were analyzed using allele-specific polymerase chain reaction in 41 pediatric recipients. Allelic prevalence was related to reference values in 65 age- and sex-matched healthy children. RESULTS Clinical data did not reveal a difference between any of the groups. HSPA1B (1267)GG genotype and HSPA1B (1267)G allele were observed more frequently in the transplant recipients compared with the control group: AA vs AG: odds ratio [OR], 12.6; 95% confidence interval [CI], 1.58-100.0; P = .004; AA vs GG: OR, 20.80; 95% CI, 2.32-187.00; P = .01; and A vs G: OR, 2.10; 95% CI, 1.19-3.07; P = .01. Furthermore, the prevalence of the HSPA1B (1267)GG genotype was greater in transplant recipients with vs without urinary tract malformations: AG vs GG: OR, 0.10; 95% CI, 0.09-0.48; P = .007. No differences were observed in the other studied polymorphisms. CONCLUSION Our findings suggest an association between the carrier status of HSPA1B (1267)G with urinary tract malformations, leading to end-stage renal disease requiring kidney transplantation. This observation raises further questions about the clinical and therapeutic relevance of this polymorphism to pediatric nephrology.

The role of Sigma-1 receptor in sex-specific heat shock response in an experimental rat model of renal ischaemia/reperfusion injury

We previously showed that female rats are more protected against renal ischaemia/reperfusion (I/R) injury than males, which is partly attributed to their more pronounced heat shock response. We recently described that Sigma‐1 receptor (S1R) activation improves postischaemic survival and renal function. 17β‐estradiol activates S1R, thus here we investigated the role of sex‐specific S1R activation and heat shock response in severe renal I/R injury. Proximal tubular cells were treated with 17β‐estradiol, which caused direct S1R activation and subsequent induction of heat shock response. Uninephrectomized female, male and ovariectomized female (Ovx) Wistar rats were subjected to 50‐min renal ischaemia followed by 2 (T2) and 24 (T24) hours of reperfusion. At T24 renal functional, impairment was less severe and structural damage was less prominent in females versus males or Ovx. Postischaemic increase in S1R, pAkt, HSF‐1, HSP72 levels were detected as early as at T2, while pHSP27 was elevated later at T24. Abundance of heat shock proteins was higher in healthy female rats and remained higher at T2 and T24 (female versus male or Ovx; resp.). We propose a S1R‐dependent mechanism, which contributes to the relative renoprotection of females after I/R injury by enhancing the heat shock response.