Genetic determinants of renal scarring in children with febrile UTI

BACKGROUND

Febrile urinary tract infections (UTIs) are among the most severe bacterial infections in infants, in which a subset of patients develops complications. Identifying infants at risk of recurrent infections or kidney damage based on clinical signs is challenging. Previous observations suggest that genetic factors influence UTI outcomes and could serve as predictors of disease severity. In this study, we conducted a nationwide survey of infant genotypes to develop a strategy for infection management based on individual genetic risk. Our aims were to identify genetic susceptibility variants for renal scarring (RS) and genetic host factors predisposing to dilating vesicoureteral reflux (VUR) and recurrent UTIs.

METHODS

To assess genetic susceptibility, we collected and analyzed DNA from blood using exome genotyping. Disease-associated genetic variants were identified through bioinformatics analysis, including allelic frequency tests and odds ratio calculations. Kidney involvement was defined using dimercaptosuccinic acid (DMSA) scintigraphy.

RESULTS

In this investigation, a cohort comprising 1087 infants presenting with their first episode of febrile UTI was included. Among this cohort, a subset of 137 infants who underwent DMSA scanning was subjected to gene association analysis. Remarkable genetic distinctions were observed between patients with RS and those exhibiting resolved kidney involvement. Notably, the genetic signature indicative of renal scarring prominently featured mitochondrial genes.

CONCLUSIONS

In this nationwide study of genetic susceptibility to RS after febrile UTIs in infancy, we identified a profile dominated by mitochondrial polymorphisms. This profile can serve as a predictor of future complications, including RS and recurrent UTIs.

Genetic polymorphisms associated with urinary tract infection in children and adults: a systematic review and meta-analysis

INTRODUCTION

The lifetime risk of urinary tract infection is known from first-degree relative studies to be highly heritable. Associations have also been observed across the life course from pediatric urinary tract infection to recurrent urinary tract infection in adulthood, suggesting lifelong susceptibility factors. Candidate gene studies and genome-wide association studies have tested for genetic associations of urinary tract infection; however, no contemporary systematic synthesis of studies is available.

OBJECTIVE

We conducted a systematic review to identify all genetic polymorphisms tested for an association with urinary tract infection in children and adults; and to assess their strength, consistency, and risk of bias among reported associations.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

PubMed, HuGE Navigator and Embase were searched from January 1, 2005 to November 16, 2023, using a combination of genetic and phenotype key words.

STUDY APPRAISAL AND SYNTHESIS METHODS

Fixed and random effects meta-analyses were conducted using codominant models of inheritance in metan. The interim Venice criteria were used to assess their credibility of pooled associations.

RESULTS

After removing 451 duplicates, 1821 studies reports were screened, with 106 selected for full-text review, 22 were included in the meta-analysis (7 adult studies and 15 pediatric studies). Our meta-analyses demonstrated significant pooled associations for pediatric urinary tract infection with variation in CXCR1, IL8, TGF, TLR4 and VDR; all of which have plausible roles in the pathogenesis of urinary tract infection. Our meta-analyses also demonstrated a significant pooled association for adult urinary tract infection with variation in CXCR1. All significant pooled associations were graded according to their epidemiological credibility, sample sizes, heterogeneity between studies, and risk of bias.

CONCLUSION

This systematic review provides a current synthesis of the known genetic architecture of urinary tract infection in childhood and adulthood; and should provide important information for researchers analysing future genetic association studies. Although, overall, the credibility of pooled associations was weak, the consistency of findings for rs2234671 single nucleotide polymorphisms of CXCR1 in both populations suggest a key role in the urinary tract infection pathogenesis.

The Impact of Infections on the Progression of Chronic Kidney Disease

Background and Objective: Infectious diseases continue to be a global burden and their impact is even worse if the patients already have other comorbidities. Because chronic kidney disease is very frequent, affecting 10% of the population, our study aims to explore the impact that infectious events have on its progression. Material and Methods: This is a retrospective, observational study based on a cohort of 238 dialyzed patients from the Nephrology Clinic of "Dr. Carol Davila" Clinical Hospital of Nephrology, Bucharest, who were followed from their first visit for five years, between 1 January 2007 and 1 January 2022. For each of them, the presence of an infectious event and the moment of the initiation of dialysis were recorded. Results: Statistical analysis showed that the patients who had at least one infectious episode were older (p = 0.004), their hemoglobin and lymphocytes were significantly lower (p = 0.03 and p = 0.02, respectively) and the time until the initiation of dialysis was lower (p = 0.007). Also, the preservation of kidney function was influenced by the number and the severity of infectious episodes. In the univariate Cox model, the following variables were associated with increased risk of dialysis: advanced age (p: 0.009; HR: 1.021; CI: 1.005 to 1.036), low hemoglobin (p: 0.001; HR: 0.861; CI: 0.786 to 0.943), previous diagnosis of chronic obstructive pulmonary disease (p: 0.002; HR: 2.467; CI: 1.376 to 4.424), presence of hematuria (p: 0.03; HR: 1.604; CI: 1.047 to 2.457) and increased values of proteinuria (p: 0.01; HR: 1.122; CI: 1.028 to 1.224) and of serum creatinine measured both at the time of the first visit and at the time of each infectious event (p: <0.001; HR: 1.262; CI: 1.141 to 1.396). Also, the presence of an infectious episode was associated with a 1.7-fold increase in the risk of dialysis initiation. The independent predictors of survival identified by the multivariate Cox model were age (p: 0.004; HR: 1.034; CI: 1.010-1.058), serum creatinine (p: <0.001; HR: 1.421; CI: 1.203 to 1.658) and proteinuria (p: <0.001; HR: 1.241; CI: 1.126 to 1.369) at the time of enrollment, but also the presence of an infectious episode during the patient's evolution (p: 0.04; HR: 1.705; CI: 1.013 to 2.868). Conclusions: In the evolution of patients with chronic kidney disease, an active search for individual factors favoring the occurrence of infectious episodes should be taken into consideration to prevent a faster progression toward end-stage kidney disease.

Chronic Kidney Disease, Urinary Tract Infections and Antibiotic Nephrotoxicity: Are There Any Relationships?

Chronic kidney disease (CKD) has been a constant burden worldwide, with a prevalence of more than 10% of the population and with mortality reaching 1.2 million deaths and 35.8 million disability-adjusted life years (DALYs) in 2017, as it is claimed by the Global Burden of Diseases. Moreover, an increase in its prevalence is expected in the next years due to a rise in the number of people suffering from obesity, diabetes mellitus and hypertension. On the other hand, with cardiovascular morbidity and mortality showing a downward trend, maybe it is time to focus on CKD, to minimize the preventable risk factors involved in its progression toward end-stage kidney disease (ESKD) and to offer a better quality of life. Another major health burden is represented by infectious diseases, particularly urinary tract infections (UTIs), as it is considered that approximately 40-50% of women and 5% of men will have at least one episode during their lifetime. Additionally, CKD consists of a constellation of immunological and metabolical disturbances that lead to a greater risk of UTIs: increased apoptosis of lymphocytes, elevated levels of tumor necrosis factor α and interleukin 6, which lower the function of neutrophils and increased levels of uremic toxins like p-cresyl sulfate and indoxyl sulfate, which alter the adherence and migration of leukocytes to the sites of injury. Moreover, UTIs can lead to a more rapid decline of kidney function, especially in stages G3-G5 of CKD, with all the complications involved. Last, but not least, antibiotherapy is often complicated in this category of patients, as antibiotics can also negatively affect the kidneys. This review will try to focus on the particularities of the urinary microbiome, asymptomatic bacteriuria and UTIs and the subtle balance between the risks of them and the risks of antibiotherapy in the evolution of CKD.

A Differential Immune Modulating Role of Vitamin D in Urinary Tract Infection

Vitamin D is known as an important modulator of numerous immune functions. We aimed to investigate the association of 25-hydroxyvitamin D [25(OH)D] with several humoral mediators of the immune system in the patients with urinary tract infection (UTI) caused by uropathogenic E. coli (UPEC). Serum levels of 25(OH)D, cytokines (interferon (IFN)-γ, interleukin (IL)-4, IL-6, IL-10, IL-17A, tumor necrosis factor transforming growth factor (TNF)-α, and tumor growth factor (TGF)-β), immunoglobulin (Ig) isotypes (IgG, IgM, and IgM), complement proteins (C3 and C4) with hemolytic activities (CH50 and AP50), and nitric oxide (NO) were evaluated in 65 patients, compared to 45 age- and sex-matched healthy controls. An insignificant decrease in 25(OH)D levels was observed in patients, compared to controls. In the patient group, elevated levels of IFN-γ, IL-17A, and IL-10 had a significant association with the serum levels of 25(OH)D, while the levels of TGF-β, IL-6, and TNF-α showed an insignificant association. The levels of IgG, C3, and NO also displayed such a statistically significant association with serum 25(OH)D levels. The AP50 levels which had significant difference were found to be not associated with serum 25(OH)D levels. Vitamin D might mediate a link between the innate and adaptive immune responses via the induction of Th1/Th17 polarization of cytokine responses and isotype regulation of antibody production, along with the maintenance of the capacity of the alternative complement pathway, in response to a UPEC infection. However, further studies are needed to validate the defined nature of the host immune response.

Biomarkers in vesicoureteral reflux: an overview

Aim: This article aimed to review the role of cytokines, chemokines, growth factors and cellular adhesion molecules as biomarkers for vesicoureteral reflux (VUR) and reflux nephropathy (RN). Methods: We reviewed articles from 1979 onward by searching PubMed and Scopus utilizing the combination of words: 'VUR' or 'RN' and each one of the biomarkers. Results: Genetic, inflammatory, fibrogenic, environmental and epigenetic factors responsible for renal scarring need to be better understood. TGF-β, IL-10, IL-6, IL-8 and TNF seem to exert a role in VUR particularly in RN based on the current literature. Serum levels of procalcitonin have been also associated with high-grade VUR and RN. These molecules should be more intensively evaluated as potential biomarkers for renal scarring in VUR. Conclusion: Further studies are necessary to define which molecules will really be of utility in clinical decisions and as therapeutic targets for VUR and RN.

An update on renal scarring after urinary tract infection in children: what are the risk factors?

AIM

The aim of this study was to present updated information on clinical, laboratory, and imaging risk factors and predictors of renal scarring after first or recurrent febrile UTIs, which may be associated with renal scarring.

METHODS

PubMed was searched for current data on possible risk factors and predictors of renal scarring after febrile urinary tract infections in children.

RESULTS

Recurrence of acute pyelonephritis is an independent risk factor for renal scarring, while the duration of fever before treatment initiation is mainly associated with acute pyelonephritis and its severity. Severe vesicoureteral reflux is an important independent risk factor for the development of renal scarring after a febrile urinary tract infection.

CONCLUSIONS

Certain clinical parameters could be used to identify children at high risk for renal scarring after febrile urinary tract infection, helping clinicians to reserve dimercaptosuccinic acid scan for selected cases.

Urinary Tract Infection in Children

BACKGROUND

Urinary Tract Infection (UTI) is a common infection in children. Prompt diagnosis and appropriate treatment are very important to reduce the morbidity associated with this condition.

OBJECTIVE

To provide an update on the evaluation, diagnosis, and treatment of urinary tract infection in children.

METHODS

A PubMed search was completed in clinical queries using the key terms "urinary tract infection", "pyelonephritis" OR "cystitis". The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews. The search was restricted to English literature and the pediatric age group. Patents were searched using the key terms "urinary tract infection" "pyelonephritis" OR "cystitis" from www.google.com/patents, http://espacenet.com, and www.freepatentsonline.com.

RESULTS

Escherichia coli accounts for 80 to 90% of UTI in children. The symptoms and signs are nonspecific throughout infancy. Unexplained fever is the most common symptom of UTI during the first two years of life. After the second year of life, symptoms and signs of pyelonephritis include fever, chills, rigor, flank pain, and costovertebral angle tenderness. Lower tract symptoms and signs include suprapubic pain, dysuria, urinary frequency, urgency, cloudy urine, malodorous urine, and suprapubic tenderness. A urinalysis and urine culture should be performed when UTI is suspected. In the work-up of children with UTI, physicians must judiciously utilize imaging studies to minimize exposure of children to radiation. While waiting for the culture results, prompt antibiotic therapy is indicated for symptomatic UTI based on clinical findings and positive urinalysis to eradicate the infection and improve clinical outcome. The choice of antibiotics should take into consideration local data on antibiotic resistance patterns. Recent patents related to the management of UTI are discussed.

CONCLUSION

Currently, a second or third generation cephalosporin and amoxicillin-clavulanate are drugs of choice in the treatment of acute uncomplicated UTI. Parenteral antibiotic therapy is recommended for infants ≤ 2 months and any child who is toxic-looking, hemodynamically unstable, immunocompromised, unable to tolerate oral medication, or not responding to oral medication. A combination of intravenous ampicillin and intravenous/intramuscular gentamycin or a third-generation cephalosporin can be used in those situations. Routine antimicrobial prophylaxis is rarely justified, but continuous antimicrobial prophylaxis should be considered for children with frequent febrile UTI.

A Putative Role of Apolipoprotein L1 Polymorphism in Renal Parenchymal Scarring Following Febrile Urinary Tract Infection in Nigerian Under-Five Children: Proposal for a Case-Control Association Study

Background

Although urinary tract infection (UTI) resolves with prompt treatment in a majority of children, some children, especially those aged less than 5 years, also develop renal parenchymal scarring (RPS). RPS causes high blood pressure that may lead to severe chronic kidney disease and end-stage renal disease (ESRD). Although the risk of UTI is higher in white children than in black children, it is unknown whether RPS is more common in white children than in black children as data are scarce in this regard. A common genetic predisposition to kidney disease in African Americans and the sub-Saharan African blacks is the possession of apolipoprotein L1 (APOL1). APOL1 risk variants regulate the production of APOL1. APOL1 circulates in the blood, and it is also found in the kidney tissue. While circulating, APOL1 kills the trypanosome parasites; an increased APOL1 in kidney tissues, under the right environmental conditions, can also result in the death of kidney tissue (vascular endothelium, the podocytes, proximal tubules, and arterial cells), which, ultimately, is replaced by fibrous tissue. APOL1 may influence the development of RPS, as evidence affirms that its expression is increased in kidney tissue following UTI caused by bacteria. Thus, UTI may be a putative environmental risk factor responsible for APOL1-induced kidney injury.

Objective

The aim of this proposal was to outline a study that seeks to determine if the possession of two copies of either G1 or G2 APOL1 variant increases the risk of having RPS, 6 months following a febrile UTI among Nigerian under-five children.

Methods

This case-control association study seeks to determine whether the risk of RPS from febrile UTI is conditional on having 2 APOL1 risk alleles (either G1 or G2). Cases will be children with a confirmed RPS following a febrile UTI. Controls will be age-, gender-, and ethnic-matched children with a febrile UTI but without RPS. Children with vesicoureteral reflux and other congenital anomalies of the urinary tract are to be excluded. Association between predictor variables (ethnicity, APOL1 G1 or G2, and others) and RPS will be tested at bivariate logistic regression analyses. Predictors that attained significance at a P value of ˂.05 will be considered for multiple logistic regressions. Likelihood-based tests will be used for hypothesis testing. Estimation will be done for the effect size for each of the APOL1 haplotypes using a generalized linear model.

Results

The study is expected to last for 3 years.

Conclusions

The study is contingent on having a platform for undergoing a research-based PhD program in any willing university in Europe or elsewhere. The findings of this study will be used to improve the care of African children who may develop RPS following febrile UTI.

Registered Report Identifier

RR1-10.2196/9514

Impact of cytokine genetic polymorphisms on the risk of renal parenchymal infection in children

BACKGROUND

Acute pyelonephritis is associated with renal scarring in up to 30% of patients. Renal scarring may cause significant long-term morbidity. The pathogenesis of acute pyelonephritis remains unclear, although it involves interaction among uroepithelium, the immune system cells, and the locally produced cytokines. That some UTI-prone children develop acute pyelonephritis, and eventually renal parenchymal scarring, suggests a genetic role. Interleukin-6, interleukin-8, chemokine receptor-1 (CXCR1), and tumor necrosis factor-alpha (TNFα), the key regulators of the host immune responses, are proteins whose secretion is controlled by genes. We postulated that functional polymorphic variants of their genes might have a role in APN susceptibility.

OBJECTIVES

We sought to investigate a possible association of the common functional polymorphisms in genes encoding IL-6, IL-8, CXCR1, and TNFα with the risk of APN in children.

METHODS

Urine culture was used to diagnose 300 children with UTI, of mean age of 51.31 ± 37.4 months (2-180 months). 99Tc-DMSA scans diagnosed 86 children with APN. Follow-up scans identified new renal scars in 18 children. Six functional single-nucleotide polymorphisms (SNPs) in genes encoding IL-6, IL-8, CXCR1, and TNFα were genotyped in all subjects (IL-6 rs1800795 (-174G/C), IL-6 rs1800796 (-572G/C), IL-8 rs2227306 (781C/T), IL8 rs4073 (-251A/T), CXCR1 rs2234671 (2607G/C), and TNFα rs1800629 (-308G/A)).

RESULTS

TT genotype of IL-8 -251A/T polymorphism was significantly higher in APN patients (26.7%) than those with lower UTI (11.7%, p = 0.01) and control individuals (12.2%, p = 0.002). T allele was significantly more common in APN than in lower UTI (p = 0.025) and was significantly more common in APN (46%) than in the controls (p = 0.001). Similarly, TT genotype of IL-8 781C/T polymorphism was significantly more common in APN patients (31.4%) than those with lower UTI (17.3%, p = 0.003) and the controls (14.3%, p = 0.001). T allele was significantly more common in APN (55%) than lower UTI (40%, p = 0.005) and controls (37%, p = 0.001). However, IL-8 -251A/T and +781C/T SNPs did not qualify as an independent risk for parenchymal infection (OR 1.9, 95% CI 0.68-2.6, p = 0.13 and OR 2.3, 95% CI 0.89-3.7, p = 0.091, respectively). Lower UTI did not differ from the controls. The frequency of the genotypes and alleles of IL-6, CXCR1, and TNFα SNPs did not differ significantly among the different groups of the study.

CONCLUSION

IL-8 -251A/T and +781C/T SNPs are associated with susceptibility to renal parenchymal infection in children and could be implicated in APN risk. However, none of these variants could clearly and independently predict this risk.

Urinary Tract Infections in Infants and Children

Urinary tract infections (UTI) are one of the most common infections in children and symptoms may be nonspecific. The risk of renal scarring is highest in children under 1 year of age with febrile UTI and high-grade vesicoureteral reflux (VUR). Although treatment of UTI is usually straightforward, given increased rates of antimicrobial resistance worldwide, the choice of treatment for pediatric UTI should be guided by community resistance patterns whenever feasible. The benefit of antimicrobial prophylaxis after first UTI and/or in the presence of VUR remains controversial, but a recent meta-analysis supports continuous antimicrobial prophylaxis in children with VUR, indicating a need for more research in this area.

Vascular endothelial growth factor-A gene polymorphism is associated with congenital renal lesions in children with urinary tract infections

AIM

This study investigated the relationship between vascular endothelial growth factor-A (VEGF-A)-460C/T functional gene polymorphism and renal parenchymal lesions, vesicoureteral reflux and other urinary tract abnormalities in children with a urinary tract infection (UTI).

METHODS

VEGF-A-460C/T gene polymorphism was investigated with restriction length polymorphism analysis in 76 children with their first UTI and in 63 controls without infections. Genotype and allele frequencies were compared between children with UTIs and controls and between different groups with UTIs.

RESULTS

The VEGF-A-460C/T genotype frequencies differed significantly between those with and without renal parenchymal lesions in the UTI cohort. Allele C homozygosity was significantly more common in those with renal parenchymal lesions (36.6% versus 8.7%, p = 0.007). A separate analysis showed that allele C was associated with lesions compatible with hypodysplasia, rather than with focal ones associated with infections, with an odds ratio of 11.55 and 95% confidence interval of 3.03-43.9 (p = 0.0001). No significant differences in genotypes or allele frequencies were found between children with and without reflux or other urinary tract anomalies.

CONCLUSION

In children with UTIs, C allele polymorphism of the VEGF-A gene was associated with hypodysplastic renal parenchymal lesions, which were possibly congenital and existed before the infection.

Susceptibility to Urinary Tract Infection: Benefits and Hazards of the Antibacterial Host Response

A paradigm shift is needed to improve and personalize the diagnosis of infectious disease and to select appropriate therapies. For many years, only the most severe and complicated bacterial infections received more detailed diagnostic and therapeutic attention as the efficiency of antibiotic therapy has guaranteed efficient treatment of patients suffering from the most common infections. Indeed, treatability almost became a rationale not to analyze bacterial and host parameters in these larger patient groups. Due to the rapid spread of antibiotic resistance, common infections like respiratory tract- or urinary-tract infections (UTIs) now pose new and significant therapeutic challenges. It is fortunate and timely that infectious disease research can offer such a wealth of new molecular information that is ready to use for the identification of susceptible patients and design of new suitable therapies. Paradoxically, the threat of antibiotic resistance may become a window of opportunity, by encouraging the implementation of new diagnostic and therapeutic approaches. The frequency of antibiotic resistance is rising rapidly in uropathogenic organisms and the molecular and genetic understanding of UTI susceptibility is quite advanced. More bold translation of the new molecular diagnostic and therapeutic tools would not just be possible but of great potential benefit in this patient group. This chapter reviews the molecular basis for susceptibility to UTI, including recent advances in genetics, and discusses the consequences for diagnosis and therapy. By dissecting the increasingly well-defined molecular interactions between bacteria and host and the molecular features of excessive bacterial virulence or host-response malfunction, it is becoming possible to isolate the defensive from the damaging aspects of the host response. Distinguishing "good" from "bad" inflammation has been a long-term quest of biomedical science and in UTI, patients need the "good" aspects of the inflammatory response to resist infection while avoiding the "bad" aspects, causing chronicity and tissue damage.

Estimation of the relationship between the polymorphisms of selected genes: ACE, AGTR1, TGFβ1 and GNB3 with the occurrence of primary vesicoureteral reflux

PURPOSE

Etiopathogenesis of VUR is composite and not fully understood. Many data indicate the importance of genetic predisposition. The aim of this study was to establish the relationship of selected polymorphisms: 14094 polymorphism of the ACE, polymorphism rs1800469 of TGFβ-1, rs5443 gene polymorphism of the GNB3 and receptor gene polymorphism rs5186 type 1 AGTR1 with the occurrence of the primary vesicoureteral reflux.

MATERIAL

The study included 190 children: 90 with the primary VUR confirmed with the voiding cystourethrogram and excluded secondary VUR and a control group of 100 children without a history of the diseases of the genitourinary tract.

METHODS

The study was planned in the scheme: "tested case versus control." Genomic DNA was isolated from the leukocytes of peripheral blood samples. The results were statistically analyzed in the Statistica 10 using χ ² test and analysis of the variance Anova.

RESULTS

Any of the four studied polymorphisms showed no difference in the distribution of genotypes between patients with primary vesicoureteral reflux and the control group. In patients with VUR and TT genotype polymorphism rs5443 GNB3 gene, the glomerular filtration rate was significantly higher than in patients with genotype CC or CT.

CONCLUSIONS

(1) No relationship was found between the studied polymorphisms (14094 ACE gene, rs1800469 gene TGFβ1, GNB3 gene rs5443, rs5186 AGTR1 gene) and the occurrence of primary vesicoureteral reflux. (2) TT genotype polymorphism rs5443 GNB3 gene may be a protective factor for the improved renal function in patients with primary vesicoureteral reflux in patients with genotype CC or CT.

The Genetics of Urinary Tract Infections and the Innate Defense of the Kidney and Urinary tract

The urinary tract is a sterile organ system. Urinary tract infections (UTIs) are common and often serious infections. Research has focused on uropathogen, environment, and host factors leading to UTI pathogenesis. A growing body of evidence exists implicating genetic factors that can contribute to UTI risks. In this review, we highlight genetic variations in aspects of the innate immune system critical to the host response to uropathogens. This overview includes genetic variations in pattern recognition receptor molecules, chemokines/cytokines, and neutrophil activation. We also comprehensively cover murine knockout models of UTI, genetic variations involved in renal scarring as a result of ascending UTIs, and asymptomatic bacteriuria.

Genetic Considerations in Pediatric Chronic Kidney Disease

Chronic kidney disease (CKD) in children is an irreversible process that, in some cases, may lead to end-stage renal disease. The majority of children with CKD have a congenital disorder of the kidney or urological tract arising from birth. There is strong evidence for both a genetic and epigenetic component to progression of CKD. Utilization of gene-mapping strategies, ranging from genome-wide association studies to single-nucleotide polymorphism analysis, serves to identify potential genetic variants that may lend to disease variation. Genome-wide association studies evaluating population-based data have identified different loci associated with CKD progression. Analysis of single-nucleotide polymorphisms on an individual level suggests that secondary systemic sequelae of CKD are closely related to dysfunction of the cardiovascular-inflammatory axis and may lead to advanced cardiovascular disease through abnormal vascular calcification and activation of the renin-angiotensin system. Similarly, genetic variants affecting cytokine control, fibrosis, and parenchymal development may modulate CKD through development and acceleration of renal interstitial fibrosis. Epigenetic studies evaluate modification of the genome through DNA methylation, histone modification, or RNA interference, which may be directly influenced by external or environmental factors directing genomic expression. Lastly, improved understanding of the genetic and epigenetic contribution to CKD progression may allow providers to identify a population at accelerated risk for disease progression and apply novel therapies targeted at the genetic mechanism of disease.

Innate immunity and genetic determinants of urinary tract infection susceptibility

Purpose of review

Urinary tract infections (UTIs) are common, dangerous and interesting. Susceptible individuals experience multiple, often clustered episodes, and in a subset of patients, infections progress to acute pyelonephritis (APN), sometimes accompanied by uro-sepsis. Others develop asymptomatic bacteriuria (ABU). Here, we review the molecular basis for these differences, with the intention to distinguish exaggerated host responses that drive disease from attenuated responses that favour protection and to highlight the genetic basis for these extremes, based on knock-out mice and clinical studies.

Recent findings

The susceptibility to UTI is controlled by specific innate immune signalling and by promoter polymorphisms and transcription factors that modulate the expression of genes controlling these pathways. Gene deletions that disturb innate immune activation either favour asymptomatic bacteriuria or create acute morbidity and disease. Promoter polymorphisms and transcription factor variants affecting those genes are associated with susceptibility in UTI-prone patients.

Summary

It is time to start using genetics in UTI-prone patients, to improve diagnosis and to assess the risk for chronic sequels such as renal malfunction, hypertension, spontaneous abortions, dialysis and transplantation. Furthermore, the majority of UTI patients do not need follow-up, but for lack of molecular markers, they are unnecessarily investigated.

Impact of common functional polymorphisms in renin angiotensin system genes on the risk of renal parenchymal scarring following childhood urinary tract infection

BACKGROUND

Pathogenesis of renal parenchymal scarring (RPS) after acute pyelonephritis (APN) is unclear. The risk of RPS varies markedly among individuals, suggesting a genetic role.

OBJECTIVE

To investigate a possible role of common polymorphisms in renin angiotensin system genes in APN-associated RPS in children.

PATIENTS AND METHODS

This study included 104 APN children and 300 controls. APN was diagnosed by urine culture and typical findings on 99Tc-DMSA scans. Voiding cystourethrogram tested the presence of vesicoureteral reflux (VUR). Follow-up DMSA scans were performed 4-6 months later to identify new RPS. Angiotensin converting enzyme gene I/D, angiotensin II receptor type-1 A1166C and angiotensinogen M235T polymorphisms were genotyped.

RESULTS

New RPS developed in 44.2% (46/104) of children with APN. VUR was diagnosed in 35.6% (37/104) of APN cases. RPS developed in 73% of cases of VUR. The D allele of ACE gene I/D polymorphism was significantly more common in APN cases with RPS (73.91%) than non-RPS (58.6%) and controls (54.5%) (p = 0.021, p = 0.002, respectively). The AGTR-1 A1166C A allele was significantly more common in VUR than the non-reflux children (91.9% versus 76.1%; p = 0.005). VUR, in contrast to the D allele (OR 6.1, 95% CI 0.878-19.7; p = 0.05), was an independent risk factor for RPS.

DISCUSSION

ACE gene D allele is associated with a twofold increase in RPS risk, which could be a result of a functional effect to increase tissue levels and activity of ACE during APN. However, D allele failed to qualify as an independent risk and its RPS association could be dependent on other co-factors, such as TGFβ1 activation, or the D-allele might link with recently discovered functional polymorphisms at the 5' end of the ACE gene. Although VUR is an independent risk for RPS, it is not clear whether this is due to exposure of the kidneys to infected urine, or VUR-associated dysplasia. In contrast with published literature, we noted higher rates of RPS and high-grade VUR, suggesting a more aggressive VUR course or local unawareness of APN. Our study has its limitations; the small number of VUR children, and the clinical and ethical difficulties of testing VCUG and DMSA in controls.

CONCLUSIONS

ACE gene D allele is associated with, but cannot independently predict, RPS in children. VUR is an independent risk for post-pyelonephritic scarring. AGTR-1 1166A/C polymorphism is associated with occurrence, but not progression, of VUR.

Discovery and functional assessment of gene variants in the vascular endothelial growth factor pathway

Angiogenesis is a host-mediated mechanism in disease pathophysiology. The vascular endothelial growth factor (VEGF) pathway is a major determinant of angiogenesis, and a comprehensive annotation of the functional variation in this pathway is essential to understand the genetic basis of angiogenesis-related diseases. We assessed the allelic heterogeneity of gene expression, population specificity of cis expression quantitative trait loci (eQTLs), and eQTL function in luciferase assays in CEU and Yoruba people of Ibadan, Nigeria (YRI) HapMap lymphoblastoid cell lines in 23 resequenced genes. Among 356 cis-eQTLs, 155 and 174 were unique to CEU and YRI, respectively, and 27 were shared between CEU and YRI. Two cis-eQTLs provided mechanistic evidence for two genome-wide association study findings. Five eQTLs were tested for function in luciferase assays and the effect of two KRAS variants was concordant with the eQTL effect. Two eQTLs found in each of PRKCE, PIK3C2A, and MAP2K6 could predict 44%, 37%, and 45% of the variance in gene expression, respectively. This is the first analysis focusing on the pattern of functional genetic variation of the VEGF pathway genes in CEU and YRI populations and providing mechanistic evidence for genetic association studies of diseases for which angiogenesis plays a pathophysiologic role.

Interactions between cytokines, congenital anomalies of kidney and urinary tract and chronic kidney disease

Fetal hydronephrosis is the most common anomaly detected on antenatal ultrasound, affecting 1-5% of pregnancies. Postnatal investigation has the major aim in detecting infants with severe urinary tract obstruction and clinically significant urinary tract anomalies among the heterogeneous universe of patients. Congenital uropathies are frequent causes of pediatric chronic kidney disease (CKD). Imaging techniques clearly contribute to this purpose; however, sometimes, these exams are invasive, very expensive, and not sufficient to precisely define the best approach as well as the prognosis. Recently, biomarkers have become a focus of clinical research as potentially useful diagnostic tools in pediatric urological diseases. In this regard, recent studies suggest a role for cytokines and chemokines in the pathophysiology of CAKUT and for the progression to CKD. Some authors proposed that the evaluation of these inflammatory mediators might help the management of postnatal uropathies and the detection of patients with high risk to developed chronic kidney disease. Therefore, the aim of this paper is to revise general aspects of cytokines and the link between cytokines, CAKUT, and CKD by including experimental and clinical evidence.

Susceptibility to acute pyelonephritis or asymptomatic bacteriuria: host-pathogen interaction in urinary tract infections

Our knowledge of the molecular mechanisms of urinary tract infection (UTI) pathogenesis has advanced greatly in recent years. In this review, we provide a general background of UTI pathogenesis, followed by an update on the mechanisms of UTI susceptibility, with a particular focus on genetic variation affecting innate immunity. The innate immune response of the host is critically important in the antibacterial defence mechanisms of the urinary tract, and bacterial clearance normally proceeds without sequelae. However, slight dysfunctions in these mechanisms may result in acute disease and tissue destruction. The symptoms of acute pyelonephritis are caused by the innate immune response, and inflammation in the urinary tract decreases renal tubular function and may give rise to renal scarring, especially in paediatric patients. In contrast, in children with asymptomatic bacteriuria (ABU), bacteria persist without causing symptoms or pathology. Pathogenic agents trigger a response determined by their virulence factors, mediating adherence to the urinary tract mucosa, signalling through Toll-like receptors (TLRs) and activating the defence mechanisms. In ABU strains, such virulence factors are mostly not expressed. However, the influence of the host on UTI severity cannot be overestimated, and rapid progress is being made in clarifying host susceptibility mechanisms. For example, genetic alterations that reduce TLR4 function are associated with ABU, while polymorphisms reducing IRF3 or CXCR1 expression are associated with acute pyelonephritis and an increased risk for renal scarring. It should be plausible to "individualize" diagnosis and therapy by combining information on bacterial virulence and the host response.

Vascular endothelial growth factor pathway polymorphisms as prognostic and pharmacogenetic factors in cancer: a systematic review and meta-analysis

Angiogenesis is an important host process that interacts with cancer cells to promote growth, invasion, and metastasis. Numerous therapeutic agents targeting the VEGF pathway have been developed. Host variability in VEGF pathway can influence angiogenesis-dependent signaling, altering sensitivity to antiangiogenic drugs and prognosis. A systematic review and meta-analysis was conducted (May 1990-July 2011). Eligible studies involved cancer patients and compared polymorphisms in the VEGF pathway [VEGF and molecules directly interacting with VEGF: KDR, FLT1, FGF, FGF2, FGFR, NRP1, endostatin (encoded by COL18A1)], and reported one of the following outcomes: overall survival, progression-free survival, time to recurrence, disease-free survival, response rate, or drug toxicity. We identified 48 cancer studies assessing prognosis and 12 cancer studies exploring pharmacogenetics of anti-VEGF therapy across various VEGF pathway polymorphisms. There was marked inter- and intradisease site heterogeneity in the effect of polymorphisms on both outcome and response to therapy. Meta-analyses of 5 VEGF polymorphisms (+936C>T, -460T>C, +405G>C, -1154G>A, and -2578C>A) identified a significant prognostic relationship: VEGF +405G>C variants showed a highly statistically significant improvement in overall survival [HR, 0.74; 95% confidence interval, 0.60-0.91; P = 0.004]. Variants (heterozygotes and/or homozygotes) of VEGF +405G>C were significantly associated with improved survival in a meta-analysis of multiple cancer sites.

The impact of therapeutic delay time on acute scintigraphic lesion and ultimate scar formation in children with first febrile UTI

We assessed the role of therapeutic delay time (TDT) in acute renal cortical scintigraphic lesion (ASL) and ultimate scar formation (USF) in children with first febrile UTI and whether it is affected by the presence of vesico-ureteral reflux (VUR). 230 children, 90 girls and 140 boys with first febrile UTI were included. Radiologic (USG, DMSA, and VCUG), clinical (age, gender, peak fever, therapeutic delay time) and laboratory (CBC with differential count, ANC (absolute neutrophil count), BUN, Creatinine, urine analysis, gram stain, culture, CRP and ESR) variables were analysed. DMSA was performed within 5 days and after six months. VCUG was performed after acute phase of UTI. The differences in TDT according to the presence of ASL, USF and VUR were assessed. And the correlation between ASL or USF with the duration of TDT was assessed. Of 230 patients enrolled, 142 patients had refluxing UTI and 88 patients had non-refluxing UTI. TDT was the risk factor associated with ASL and USF along with presence of VUR. TDT was longer in ASL positive group compared with the ASL negative group. Also USF group showed longer TDT compared with those without USF in both refluxing UTI and non refluxing UTI. The TDT was significantly shorter in USF group with the presence of VUR. Positive linear association was noted between prevalence of ASL and USF and duration of TDT. In conclusion, the impact of UTI on formation of USF may be enhanced by the presence of VUR with shorter duration of TDT.

Genetics of innate immunity and UTI susceptibility

A functional and well-balanced immune response is required to resist most infections. Slight dysfunctions in innate immunity can turn the 'friendly' host defense into an unpleasant foe and give rise to disease. Beneficial and destructive forces of innate immunity have been discovered in the urinary tract and mechanisms by which they influence the severity of urinary tract infections (UTIs) have been elucidated. By modifying specific aspects of the innate immune response to UTI, genetic variation either exaggerates the severity of acute pyelonephritis to include urosepsis and renal scarring or protects against symptomatic disease by suppressing innate immune signaling, as in asymptomatic bacteriuria (ABU). Different genes are polymorphic in patients prone to acute pyelonephritis or ABU, respectively, and yet discussions of UTI susceptibility in clinical practice still focus mainly on social and behavioral factors or dysfunctional voiding. Is it not time for UTIs to enter the era of molecular medicine? Defining why certain individuals are protected from UTI while others have severe, recurrent infections has long been difficult, but progress is now being made, encouraging new approaches to risk assessment and therapy in this large and important patient group, as well as revealing promising facets of 'good' versus 'bad' inflammation.

Genetic susceptibility to renal scar formation after urinary tract infection: a systematic review and meta-analysis of candidate gene polymorphisms

Identifying patients who may develop renal scarring after urinary tract infections (UTI) remains challenging, as clinical determinants explain only a portion of individual risk. An additional factor that likely affects risk is individual genetic variability. We searched for peer-reviewed articles from 1980 to December 2009 in electronic databases that reported results showing an association between gene polymorphims and renal scaring after UTI. Two independent researchers screened articles using predetermined criteria. Studies were assessed for methodological quality using an aggregate scoring system. The 18 studies ultimately included in the review had investigated 16 polymorphisms in nine genes in association with renal scarring formation after UTI. Based on the predetermined criteria for assessing the quality of the studies, 12 studies (67%) were identified as being of poor quality design. A meta-analysis of cumulative studies showed on association between renal scarring formation after UTI and the angiotensin converting enzyme insertion/deletion polymorphism [ACE I/D; recessive model for D allele; odds ratio (OR) 1.73, 95% confidence interval (CI) 1.09-2.74, P = 0.02] or transforming growth factor (TGF)-β1 c.-509 T > C polymorphism (dominant model for T allele; OR 2.24, 95% CI 1.34-3.76, P = 0.002). However, heterogeneity among studies was large, indicating a strong difference that cannot only be explained by differences in study design. The studies reviewed in this article support a modest involvement of the vasomotor and inflammatory genes in the development of renal scarring after UTIs. This review also shows that only few possible candidate genes have been investigated for an association with renal scarring, raising the hypothesis that some gene polymorphisms may exert their effects through an interaction with as yet uninvestigated factors that may be related to geographic and/or socio-economic differences.