Renal cytokine responses in acute Escherichia coli pyelonephritis in IL-6-deficient mice

Role of N-acetylkynurenine in mediating the effect of gut microbiota on urinary tract infection: a Mendelian randomization study

Introduction

This study explored the causal connections between gut microbiota (GM), urinary tract infection (UTI), and potential metabolite mediators using Mendelian randomization (MR).

Methods

We utilized summary statistics from the most comprehensive and extensive genome-wide association studies (GWAS) available to date, including 196 bacterial traits for GM, 1,091 blood metabolites, 309 metabolite ratios, alongside UTI data from ukb-b-8814 and ebi-a-GCST90013890. Bidirectional MR analyses were conducted to investigate the causal links between GM and UTI. Subsequently, two MR analyses were performed to identify the potential mediating metabolites, followed by a two-step MR analysis to quantify the mediation proportion.

Results

Our findings revealed that out of the total 15 bacterial traits, significant associations with UTI risk were observed across both datasets. Particularly, taxon g_Ruminococcaceae UCG010 displayed a causal link with a diminished UTI risk in both datasets (ukb-b-8814: odds ratio [OR] = 0.9964, 95% confidence interval [CI] = 0.9930-0.9997, P = 0.036; GCST90013890: OR = 0.8252, 95% CI = 0.7217-0.9436, P = 0.005). However, no substantial changes in g_Ruminococcaceae UCG010 due to UTI were noted (ukb-b-8814: β = 0.51, P = 0.87; ebi-a-GCST90013890: β = -0.02, P = 0.77). Additionally, variations in 56 specific metabolites were induced by g_Ruminococcaceae UCG010, with N-acetylkynurenine (NAK) exhibiting a causal correlation with UTI. A negative association was found between g_Ruminococcaceae UCG010 and NAK (OR: 0.8128, 95% CI: 0.6647-0.9941, P = 0.044), while NAK was positively associated with UTI risk (OR: 1.0009; 95% CI: 1.0002-1.0016; P = 0.0173). Mediation analysis revealed that the association between g_Ruminococcaceae UCG010 and UTI was mediated by NAK with a mediation proportion of 5.07%.

Discussion

This MR study provides compelling evidence supporting the existence of causal relationships between specific GM taxa and UTI, along with potential mediating metabolites.

Supraphysiologic Vaginal Estrogen Therapy in Aged Mice Mitigates Age-Associated Bladder Inflammatory Response to Urinary Tract Infections

IMPORTANCE

Bladder diseases characterized by chronic inflammation are highly prevalent in older women, as are recurrent urinary tract infections (rUTIs). Recurrent urinary tract infections lead to chronic inflammation of the bladder mucosa and cause lower urinary tract symptoms that persist even after the infection is cleared. Vaginal estrogen therapy (VET) has long been used for the treatment of rUTIs; however, its mechanism of action remains unclear.

OBJECTIVES

The objective of this study was to examine the mechanism(s) by which VET affects bladder inflammation and response to rUTIs.

STUDY DESIGN

Here, we induced surgical menopause in aged (18 months old) mice followed by VET. Mice were then infected with uropathogenic Escherichia coli , and course of infection was investigated. Inflammatory cytokine response was assessed before and during infection using enzyme-linked immunosorbent assay. RNA sequencing analysis was used to compare the inflammatory status of the young versus aged bladder and principal changes confirmed via quantitative reverse transcriptase-polymerase chain reaction to determine the effects of VET on bladder inflammation. Impact on age-associated bladder tertiary lymphoid tissue formation was evaluated histologically.

RESULTS

In the ovariectomized aged model, VET not only mitigated uterine atrophy but was also associated with reduced rUTIs, number of bacterial reservoirs, dampened immune response, and promotion of terminal differentiation of urothelial cells. Bladder tertiary lymphoid tissue lesions were also reduced with VET, with an associated decrease in signals important for bladder tertiary lymphoid tissue formation. Finally, we determined that VET reverses age-associated upregulation of inflammatory genes and pathways.

CONCLUSIONS

Our data suggest that VET is effective by reducing age-associated hyperinflammatory conditions in bladder mucosa and in enhancing the host response to infection.

Trimethylamine N-Oxide (TMAO) Mediates Increased Inflammation and Colonization of Bladder Epithelial Cells during a Uropathogenic E. coli Infection In Vitro

Urinary tract infections (UTIs) are among the most common infections in humans and are often caused by uropathogenic E. coli (UPEC). Trimethylamine N-oxide (TMAO) is a proinflammatory metabolite that has been linked to vascular inflammation, atherosclerosis, and chronic kidney disease. As of today, no studies have investigated the effects of TMAO on infectious diseases like UTIs. The aim of this study was to investigate whether TMAO can aggravate bacterial colonization and the release of inflammatory mediators from bladder epithelial cells during a UPEC infection. We found that TMAO aggravated the release of several key cytokines (IL-1β and IL-6) and chemokines (IL-8, CXCL1 and CXCL6) from bladder epithelial cells during a CFT073 infection. We also found that CFT073 and TMAO mediate increased release of IL-8 from bladder epithelial cells via ERK 1/2 signaling and not bacterial growth. Furthermore, we showed that TMAO enhances UPEC colonization of bladder epithelial cells. The data suggest that TMAO may also play a role in infectious diseases. Our results can be the basis of further research to investigate the link between diet, gut microbiota, and urinary tract infection.

DIA mass spectrometry characterizes urinary proteomics in neonatal and adult donkeys

Health monitoring is critical for newborn animals due to their vulnerability to diseases. Urine can be not only a useful and non-invasive tool (free-catch samples) to reflect the physiological status of animals but also to help monitor the progression of diseases. Proteomics involves the study of the whole complement of proteins and peptides, including structure, quantities, functions, variations and interactions. In this study, urinary proteomics of neonatal donkeys were characterized and compared to the profiles of adult donkeys to provide a reference database for healthy neonatal donkeys. The urine samples were collected from male neonatal donkeys on their sixth to tenth days of life (group N) and male adult donkeys aging 4-6 years old (group A). Library-free data-independent acquisition (direct DIA) mass spectrometry-based proteomics were applied to analyze the urinary protein profiles. Total 2179 urinary proteins were identified, and 411 proteins were differentially expressed (P < 0.05) between the two groups. 104 proteins were exclusively expressed in group N including alpha fetoprotein (AFP), peptidase-mitochondrial processing data unit (PMPCB), and upper zone of growth plate and cartilage matrix associated (UCMA), which might be used to monitor the health status of neonatal donkeys. In functional analysis, some differentially expressed proteins were identified related to immune system pathways, which might provide more insight in the immature immunity of neonatal donkeys. To the best of our knowledge, this is the first time to report donkey urinary proteome and our results might provide reference for urinary biomarker discovery used to monitor and evaluate health status of neonatal donkeys.

The role of uropathogenic Escherichia coli adhesive molecules in inflammatory response- comparative study on immunocompetent hosts and kidney recipients

Background

Urinary tract infections (UTI) represent one of the most common contagious diseases in humans. Uropathogenic Escherichia coli (UPEC) strains are recognized as the most frequent causative agent, and these express a range of virulence factors including the adhesins. Immune response to UPEC under immunosuppression has not been fully understood yet. Interleukin 1β (IL1β), 6 (IL6) and 17 (IL17) represent clinically relevant markers of inflammation.

Aim

The study aimed to investigate the interplay between UPEC genotype and hosts’ immune status in shaping local inflammatory response in the course of an UTI episode. The respective numbers of: 18 kidney recipients with UPEC UTI, 28 immunocompetent hosts with UPEC UTI and 29 healthy controls were involved. Urine IL1β, IL6, and IL17/creatinine ratios in relation to fimH, csgA, papC, tosA, and flu genes presence in UPEC isolated from the urine samples were analyzed. Apart from traditional statistics, also machine learning algorithms were applied.

Results

The urine levels of IL1β and IL 6 were similar in kidney recipients and the immunocompetent hosts. IL1β levels were higher in both kidney recipients and immunocompetent hosts than in controls, while IL6 levels were higher only in immunocompetent hosts than in controls. In the machine learning classification model, high urine IL17 levels were significantly more prevalent in controls, while low IL17 levels in urines infected with Ag43-positive UPEC strains, regardless of the host’s immune status. In the traditional statistical analysis, IL17 levels appeared significantly higher in urine samples from kidney recipients infected with Ag43–negative UPEC strains.

Conclusions

In the UTI- affected patients, the combination of the immune status of an individual and Ag43 status of the UPEC strain determined urine IL17 level in the analyzed group. However, IL17 levels above median were overall more prevalent in controls.

Human Renal Fibroblasts, but Not Renal Epithelial Cells, Induce IL-1β Release during a Uropathogenic Escherichia coli Infection In Vitro

Understanding how uropathogenic Escherichia coli (UPEC) modulates the immune response in the kidney is essential to prevent UPEC from reaching the bloodstream and causing urosepsis. The purpose of this study was to elucidate if renal fibroblasts can release IL-1β during a UPEC infection and to investigate the mechanism behind the IL-1β release. We found that the UPEC strain CFT073 induced an increased IL-1β and LDH release from renal fibroblasts, but not from renal epithelial cells. The UPEC-induced IL-1β release was found to be NLRP3, caspase-1, caspase-4, ERK 1/2, cathepsin B and serine protease dependent in renal fibroblasts. We also found that the UPEC virulence factor α-hemolysin was necessary for IL-1β release. Conditioned medium from caspase-1, caspase-4 and NLRP3-deficient renal fibroblasts mediated an increased reactive oxygen species production from neutrophils, but reduced UPEC phagocytosis. Taken together, our study demonstrates that renal fibroblasts, but not renal epithelial cells, release IL-1β during a UPEC infection. This suggest that renal fibroblasts are vital immunoreactive cells and not only structural cells that produce and regulate the extracellular matrix.

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.

Trans IL-6 signaling does not appear to play a role in renal scarring after urinary tract infection

INTRODUCTION

While inflammation is an important innate defense mechanism against infection, it can also lead to local tissue damage. The trans signaling pathway of interleukin (IL)-6 is a known mediator of inflammation. We hypothesized that the trans IL-6 signaling pathway is associated with the development of post febrile urinary tract infection (UTI) renal scarring.

OBJECTIVE

To compare soluble regulators of trans IL-6 signaling between patients with a history of febrile UTI who do or do not have renal scarring.

STUDY DESIGN

After IRB-approval, we collected urine samples in pediatric patients with a history of febrile (≥38 °C) UTI (urine culture >50 K uropathogen) with documented presence or absence of renal scarring on imaging. Samples were collected at a time when patients were not actively infected. Enzyme-linked immunosorbent assays were performed on samples for markers of trans IL-6 signaling: IL-6, soluble (s) IL-6 receptor (R), and soluble (s)gp130, a buffer in trans IL-6 signaling. Values were normalized to urine creatinine. Results were analyzed by t-test or Mann-Whitney U. Spearman rank correlation was used. A p-value of <0.05 was considered significant.

RESULTS

A total of 50 urines from patients with a history of febrile UTI were collected: 23 with and 27 without scarring. There was no difference between groups regarding age or gender. There was no significant difference in urine IL-6, sIL-6R, or sgp130 between those with and without scarring (Figure). While IL-6 values significantly correlated with sIL-6R and sgp130 in those without renal scarring, IL-6 did not correlate with sgp130 in those with scarring. Ratios of IL-6 to sgp130 and sIL-6R to sgp130 were not different between groups.

DISCUSSION

The inflammatory response generated in response to infection is believed to be largely responsible for the development of renal scarring after UTI. IL-6 is a cytokine known to be induced during UTI with a pro-inflammatory pathway, known as trans signaling. This study investigated for differences in markers of trans IL-6 signaling between patients with a history of febrile UTI with and without renal scarring. There was no significant difference between the absolute values or ratio of these markers between groups.

CONCLUSIONS

Markers of trans IL-6 signaling are not different between individuals with a history of febrile UTI with and without renal scarring in the non-acute setting.

Innate immunity and urinary tract infection

Urinary tract infections are a severe public health problem. The emergence and spread of antimicrobial resistance among uropathogens threaten to further compromise the quality of life and health of people who develop acute and recurrent upper and lower urinary tract infections. The host defense mechanisms that prevent invasive bacterial infection are not entirely delineated. However, recent evidence suggests that versatile innate immune defenses play a key role in shielding the urinary tract from invading uropathogens. Over the last decade, considerable advances have been made in defining the innate mechanisms that maintain immune homeostasis in the kidney and urinary tract. When these innate defenses are compromised or dysregulated, pathogen susceptibility increases. The objective of this review is to provide an overview of how basic science discoveries are elucidating essential innate host defenses in the kidney and urinary tract. In doing so, we highlight how these findings may ultimately translate into the clinic as new biomarkers or therapies for urinary tract infection.

Impact of Proinflammatory Cytokines on the Virulence of Uropathogenic Escherichia coli

The effect of a urinary tract infection on the host is a well-studied research field. However, how the host immune response affects uropathogenic Escherichia coli (CFT073) virulence is less studied. The aim of the present study was to investigate the impact of proinflammatory cytokine exposure on the virulence of uropathogenic Escherichia coli. We found that all tested proinflammatory cytokines (TNF-α, IL-1β, IL-6, IL-8 and IFN-γ) induced an increased CFT073 growth. We also found that biofilm formation and hemolytic activity was reduced in the presence of all proinflammatory cytokines. However, a reduction in siderophore release was only observed in the presence of IL-1β, IL-6 and IL-8. Real time-qPCR showed that all proinflammatory cytokines except TNF-α significantly increased genes associated with the iron acquisition system in CFT073. We also found that the proinflammatory cytokines induced significant changes in type-1 fimbriae, P-fimbriae and gluconeogenetic genes. Furthermore, we also showed, using a Caenorhabditis elegans (C. elegans) killing assay that all cytokines decreased the survival of C. elegans worms significantly. Taken together, our findings show that proinflammatory cytokines have the ability to alter the virulence traits of UPEC.

Host-Derived Nitric Oxide and Its Antibacterial Effects in the Urinary Tract

Urinary tract infection (UTI) is one of the most common bacterial infections in humans, and the majority are caused by uropathogenic Escherichia coli (UPEC). The rising antibiotic resistance among UPEC and the frequent failure of antibiotics to effectively treat recurrent UTI and catheter-associated UTI motivate research on alternative ways of managing UTI. Abundant evidence indicates that the toxic radical nitric oxide (NO), formed by activation of the inducible nitric oxide synthase, plays an important role in host defence to bacterial infections, including UTI. The major source of NO production during UTI is from inflammatory cells, especially neutrophils, and from the uroepithelial cells that are known to orchestrate the innate immune response during UTI. NO and reactive nitrogen species have a wide range of antibacterial targets, including DNA, heme proteins, iron-sulfur clusters, and protein thiol groups. However, UPEC have acquired a variety of defence mechanisms for protection against NO, such as the NO-detoxifying enzyme flavohemoglobin and the NO-tolerant cytochrome bd-I respiratory oxidase. The cytotoxicity of NO-derived intermediates is nonspecific and may be detrimental to host cells, and a balanced NO production is crucial to maintain the tissue integrity of the urinary tract. In this review, we will give an overview of how NO production from host cells in the urinary tract is activated and regulated, the effect of NO on UPEC growth and colonization, and the ability of UPEC to protect themselves against NO. We also discuss the attempts that have been made to develop NO-based therapeutics for UTI treatment.

Activation of the NLRP3 Inflammasome Pathway by Uropathogenic Escherichia coli Is Virulence Factor-Dependent and Influences Colonization of Bladder Epithelial Cells

The NLRP3 inflammasome and IL-1β release have recently been suggested to be important for the progression of urinary tract infection (UTI). However, much is still unknown regarding the interaction of UPEC and the NLRP3 inflammasome. The purpose of this study was to elucidate what virulence factors uropathogenic Escherichia coli (UPEC) use to modulate NLRP3 inflammasome activation and subsequent IL-1β release and the role of NLRP3 for UPEC colonization of bladder epithelial cells. The bladder epithelial cell line 5637, CRISPR/Cas9 generated NLRP3, caspase-1 and mesotrypsin deficient cell lines and transformed primary bladder epithelial cells (HBLAK) were stimulated with UPEC isolates and the non-pathogenic MG1655 strain. We found that the UPEC strain CFT073, but not MG1655, induced an increased caspase-1 activity and IL-1β release from bladder epithelial cells. The increase was shown to be mediated by α-hemolysin activation of the NLRP3 inflammasome in an NF-κB-independent manner. The effect of α-hemolysin on IL-1β release was biphasic, initially suppressive, later inductive. Furthermore, the phase-locked type-1-fimbrial ON variant of CFT073 inhibited caspase-1 activation and IL-1β release. In addition, the ability of CFT073 to adhere to and invade NLRP3 deficient cells was significantly reduced compare to wild-type cells. The reduced colonization of NLRP3-deficient cells was type-1 fimbriae dependent. In conclusion, we found that the NLRP3 inflammasome was important for type-1 fimbriae-dependent colonization of bladder epithelial cells and that both type-1 fimbriae and α-hemolysin can modulate the activity of the NLRP3 inflammasome.

Interleukin-6/Stat3 signaling has an essential role in the host antimicrobial response to urinary tract infection

The signaling networks regulating antimicrobial activity during urinary tract infection (UTI) are incompletely understood. Interleukin-6 (IL-6) levels increase with UTI severity, but the specific contributions of IL-6 to host immunity against bacterial uropathogens are unknown. To clarify this we tested whether IL-6 activates the Stat3 transcription factor, to drive a program of antimicrobial peptide gene expression in infected urothelium during UTI. Transurethral inoculation of uropathogenic Escherichia coli led to IL-6 secretion, urothelial Stat3 phosphorylation, and activation of antimicrobial peptide transcription, in a Toll-like receptor 4-dependent manner in a murine model of cystitis. Recombinant IL-6 elicited Stat3 phosphorylation in primary urothelial cells in vitro, and systemic IL-6 administration promoted urothelial Stat3 phosphorylation and antimicrobial peptide expression in vivo. IL-6 deficiency led to decreased urothelial Stat3 phosphorylation and antimicrobial peptide mRNA expression following UTI, a finding mirrored by conditional Stat3 deletion. Deficiency in IL-6 or Stat3 was associated with increased formation of intracellular bacterial communities, and exogenous IL-6 reversed this phenotype in IL-6 knockout mice. Moreover, chronic IL-6 depletion led to increased renal bacterial burden and severe pyelonephritis in C3H/HeOuJ mice. Thus, IL-6/Stat3 signaling drives a transcriptional program of antimicrobial gene expression in infected urothelium, with key roles in limiting epithelial invasion and ascending infection.

[Ca2+]i Oscillations and IL-6 Release Induced by α-Hemolysin from Escherichia coli Require P2 Receptor Activation in Renal Epithelia

Urinary tract infections are commonly caused by α-hemolysin (HlyA)-producing Escherichia coli. In erythrocytes, the cytotoxic effect of HlyA is strongly amplified by P2X receptors, which are activated by extracellular ATP released from the cytosol of the erythrocytes. In renal epithelia, HlyA causes reversible [Ca(2+)]i oscillations, which trigger interleukin-6 (IL-6) and IL-8 release. We speculate that this effect is caused by HlyA-induced ATP release from the epithelial cells and successive P2 receptor activation. Here, we demonstrate that HlyA-induced [Ca(2+)]i oscillations in renal epithelia were completely prevented by scavenging extracellular ATP. In accordance, HlyA was unable to inflict any [Ca(2+)]i oscillations in 132-1N1 cells, which lack P2R completely. After transfecting these cells with the hP2Y2 receptor, HlyA readily triggered [Ca(2+)]i oscillations, which were abolished by P2 receptor antagonists. Moreover, HlyA-induced [Ca(2+)]i oscillations were markedly reduced in medullary thick ascending limbs isolated from P2Y2 receptor-deficient mice compared with wild type. Interestingly, the following HlyA-induced IL-6 release was absent in P2Y2 receptor-deficient mice. This suggests that HlyA induces ATP release from renal epithelia, which via P2Y2 receptors is the main mediator of HlyA-induced [Ca(2+)]i oscillations and IL-6 release. This supports the notion that ATP signaling occurs early during bacterial infection and is a key player in the further inflammatory response.

Association of interleukin-10 gene promoter polymorphisms with susceptibility to acute pyelonephritis in children

Interleukin-10 (IL-10) is a potent inhibitor of leukocyte chemotaxis, bacterial killing in phagocytes and synthesis of pro-inflammatory cytokines and chemokines, and recent studies have suggested an important role for this immunoregulatory cytokine in the pathogenesis of urinary tract infections (UTIs). Therefore, the gene encoding IL-10 (IL10) is an attractive candidate for association studies attempting to identify susceptibility genes conferring risk of UTIs. In this case-control study, we aimed to investigate the association of single nucleotide polymorphisms (SNPs) in the promoter region of IL10 with acute pyelonephritis in the Slovak population. Polymerase chain reaction with sequence-specific primers was used to analyse IL10 -1082A/G (rs1800896), -819C/T (rs1800871) and -592C/A (rs1800872) SNPs in 147 children with acute pyelonephritis and 215 healthy controls. Comparison of patients with healthy controls using the logistic regression analysis revealed significantly increased risk of developing recurrent attacks of acute pyelonephritis for -1082 G allele in a dominant genetic model GG (GG + AG vs. AA, P = 0.019, odds ratio (OR) = 2.26). A similar tendency was also found when the recurrent acute pyelonephritis subgroup was compared to episodic pyelonephritis cases (GG + AG vs. AA, P = 0.009, OR = 3.38). In conclusion, our results suggest that IL10 -1082 A/G SNP is a susceptibility factor for development of recurrent attacks of acute pyelonephritis.

Toll-like receptor 2 down-regulation in established mouse allergic lungs contributes to decreased mycoplasma clearance

RATIONALE

Respiratory Mycoplasma pneumoniae (Mp) infection is involved in asthma pathobiology, but whether the established allergic airway inflammation compromises lung innate immunity and subsequently predisposes patients with asthma to Mp infection remains unknown.

OBJECTIVES

To test whether the established allergic airway inflammation compromises host innate immunity (e.g., Toll-like receptor 2 [TLR2]) to hinder the elimination of Mp from the lungs.

METHODS

We used mouse models of ovalbumin (OVA)-induced allergic airway inflammation with an ensuing Mp infection, and cultures of mouse primary lung dendritic cells (DCs) and bone marrow-derived DCs.

MEASUREMENTS AND MAIN RESULTS

Lung Mp clearance in allergic mice and TLR2 and IL-6 levels in lung cells, including DCs as well as cultured primary lung DCs and bone marrow-derived DCs, were assessed. The established OVA-induced allergic airway inflammation, or the prominent Th2 cytokines IL-4 and IL-13, inhibited TLR2 expression and IL-6 production in lung cells, including lung DCs, and eventually led to impaired host defense against Mp. Studies in IL-6 knockout mice indicated that IL-6 directly promoted Mp clearance from the lungs. IL-4- and IL-13-induced suppression of TLR2 was mediated by inhibiting nuclear factor-kappaB activation through signal transducer and activator of transcription 6 (STAT6) signaling pathway.

CONCLUSIONS

The established OVA-induced allergic airway inflammation impairs TLR2 expression and host defense cytokine (e.g., IL-6) production, and subsequently delays lung bacterial clearance. This could offer novel therapeutic strategies to reinstate TLR2 activation by using TLR2 ligands and/or blocking IL-4 and IL-13 to ameliorate persisting respiratory bacterial infections in allergic lungs.

Serum and urine interleukin-6 and transforming growth factor-beta1 in young infants with pyelonephritis

BACKGROUND

Cytokines are involved both in the acute response during pyelonephritis and in the progression to renal scarring. The aim of the present study was to assess the pro-inflammatory interleukin-6 (IL-6) and the anti-inflammatory pro-fibrotic transforming growth factor-beta1 (TGF-beta) in very young infants with pyelonephritis.

METHODS

Serum and urine concentrations of IL-6 and TGF-beta1 were determined by enzyme immunoassay in infants with acute pyelonephritis before antibiotic treatment and in infants with non-renal fever. IL-6 was studied in 12 infants with pyelonephritis and in eight with non-renal fever (median ages, 2 months for both groups). TGF-beta1 was studied in 11 infants with pyelonephritis and in nine with non-renal fever (median ages, 2 and 4 months, respectively).

RESULTS

No significant differences were documented in serum concentrations of IL-6 and TGF-beta1 between patients and controls. Urine IL-6 levels were significantly higher in infants with pyelonephritis than in controls (medians, 147 and 21.4 pg/ml, respectively; P = 0.0106). The urine levels of TGF-beta1 were lower in infants with pyelonephritis than in controls, although not significantly (medians, 6.12 and 11.0 ng/ml, respectively; P = 0.0705).

CONCLUSIONS

Our findings confirm the implication of IL-6 but not of TGF-beta1 in the pathogenesis of the early stages of pyelonephritis in young infants. Tauhe role of the pro-fibrotic TGF-beta1 in the development of renal scarring deserves further investigation.

Obesity and inflammation in children

Systemic inflammation is present in children and adults with obesity. Inflammation associated with obesity appears to be central to the development of insulin resistance and atherosclerosis and may be important in the pathogenesis of other comorbid conditions. Although generally considered an inert energy storage tissue, white adipose tissue is a metabolically active organ. It produces a number of inflammatory cytokines and acute-phase reactants. Inflammation associated with obesity declines after weight loss and with exercise. It may also be possible to modify obesity-associated inflammation with medications, reducing comorbidities without weight loss. The study of inflammation in the context of excessive adipose tissue is central to understanding obesity and modifying its impact on patients.

Pathophysiology, Diagnosis, and Management of Urinary Tract Infection in Horses

Equine urinary tract infection (UTI) most commonly occurs as a sequela to structural or functional inhibition of normal urine flow. Although it is an infrequent diagnosis in equids, the incidence of UTI in human beings is high and has inspired great investigative effort. The resultant findings with potentially broad application as well as current equine studies are reviewed here. Recent developments in the understanding of host-agent interactions and renal defense mechanisms, emerging antimicrobial resistance, and novel therapeutic alternatives to prophylactic antibiotic use are emphasized.

Urine Cytokines Profile in Renal Transplant Patients with Asymptomatic Bacteriuria

BACKGROUND

The role of asymptomatic bacteriuria in kidney transplant recipients is unknown. There is no clear evidence of its effect on transplanted kidney.

METHODS

We studied urine cytokines profile among kidney transplant recipients with bacteriuria found in screening examination. Urine cultures were collected in 269 patients with stable graft function and serum creatinine level <2 mg/dl, during their routine visits. Interleukin (IL)-6 and IL-8 levels were measured in urine samples from patients with asymptomatic bacteriuria, symptomatic urinary tract infection and patients without bacteriuria (control group). Changes in serum creatinine level in patients with asymptomatic bacteriuria and in the control group were observed during 12 months follow up.

RESULTS

Urinary tract infection (UTI) was diagnosed in five patients and asymptomatic bacteriuria in 22 patients. Urine IL-6 level was significantly higher in symptomatic UTI group (median 15.71 pg/mg) but there were no differences between group of patients with asymptomatic bacteriuria (3.92 pg/mg) and control group (2.54 pg/mg). Urine IL-8 level was higher in symptomatic UTI group (median 146.8 pg/mg) and was also significantly higher in asymptomatic bacteriuria group (33.49 pg/mg) in comparison to control group (2.97 pg/mg; P=0.0002). During 1-year follow up, incidence of UTI was higher in the asymptomatic bacteriuria group than in the control group but graft function was not different in both groups.

CONCLUSIONS

Elevated urine IL-8 level in kidney transplant patients with asymptomatic bacteriuria may reflect impaired immune response to bacterial infection and occult inflammatory process in urinary tract.

Pathogenesis of urinary tract infection: an update

PURPOSE OF REVIEW

Urinary tract infection is the second most common bacterial infection in children. It may cause renal scarring leading to secondary hypertension and chronic kidney disease. Recent information has greatly improved our understanding of the pathogenesis of urinary tract infection and renal scarring.

RECENT FINDINGS

Urothelium, an anatomical barrier for innate immune responses, expresses toll-like receptors with the capacity to recognize pathogen-associated molecular patterns. Engagement of toll-like receptors can lead to uroepithelial cell activation and production of inflammatory mediators. These include complement proteins, other bactericidal peptides, cytokines, chemokines, defensins and adhesion molecules. The resulting inflammatory infiltrate serves to aid bacterial clearance but can also lead to renal damage. Furthermore, interactions between urinary proteins, such as Tamm-Horsfall protein, and TLR-4 add to the complexity of this defense system. Interindividual variability in cellular response may in part be responsible for variable clinical outcomes. Polymorphisms in a number of candidate genes in this host defense mechanism may be involved in determining those patients who are susceptible to recurrent infections and renal scarring following urinary tract infection.

SUMMARY

Further understanding of the basic molecular mechanisms of urinary tract infection and translating these bench data to the bedside holds the promise of improving diagnosis and therapeutic strategies of treating urinary tract infection and preventing recurrence and renal scarring.

Dose-dependent induction of IL-6 by plant-derived proteases in vitro

Oral administration of proteases such as bromelain and papain is commonly used in patients with a wide range of inflammatory conditions, but their molecular and cellular mechanisms of action are still poorly understood. The aim of our study was to investigate the impact of these proteases on the release of interleukin-6 (IL-6) and other cytokines in the recently described modified mixed lymphocyte culture (MMLC) test system which is based on the mutual interaction of cells of the innate and adaptive immunity. Bromelain and papain enhanced IL-6 production dose-dependently up to 400-fold in MMLC before and up to 30-fold after neutralization of LPS content of proteases using polymyxin B, indicating that IL-6 induction by protease treatment was attributable to both protease action and LPS content of enzyme preparations. The production of IFNgamma and IL-10 was not altered by bromelain or papain, indicating a selective and differential immune activation. Both proteases impaired cytokine stability, cell proliferation and expression of cell surface molecules like CD14 only marginally, suggesting no impact of these mechanisms on protease-mediated cytokine release. These findings might provide the mechanistic rationale for the current use of proteases in wound healing and tissue regeneration since these processes depend on IL-6 induction.

Roles of interleukin-6 in activation of STAT proteins and recruitment of neutrophils during Escherichia coli pneumonia

Interleukin (IL)-6 concentrations are positively associated with the severity of pneumonia, and this cytokine is essential to surviving experimental pneumococcal pneumonia. The role that IL-6 plays during pneumonia and its impact during gram-negative bacterial pneumonia remain to be determined. During Escherichia coli pneumonia, IL-6-deficient mice had increased bacterial burdens in their lungs, indicating compromised host defenses. Decreased neutrophil counts in alveolar air spaces, despite normal blood neutrophil counts and survival of emigrated neutrophils, suggested that defective neutrophil recruitment was responsible for exacerbating the infection. Neutrophil recruitment requires nuclear factor (NF)- kappa B, but IL-6 was neither sufficient nor essential to induce NF- kappa B-mediated gene expression in the lungs. In contrast, IL-6 induced the phosphorylation of signal transducer and activator of transcription (STAT) 1 and STAT3 in the lungs, and STAT1 and STAT3 phosphorylation during E. coli pneumonia was decreased by IL-6 deficiency. Thus, IL-6 plays essential roles in activating STAT transcription factors, enhancing neutrophil recruitment, and decreasing bacterial burdens during E. coli pneumonia.

Imaging Techniques for the Study of Escherichia coli and Salmonella Infections

Infectious diseases are among the leading causes of mortality worldwide, and numerous bacterial species are included in the vast array of causative agents. This review describes microscopy-based techniques that can be used to study interactions between bacteria and infected host cells, bacterial gene expression in the infected animal, and bacteria-induced cell signaling in eukaryotic cells. As infectious model systems, urinary tract infections caused by uropathogenic Escherichia coli (UPEC) and a mouse model of typhoid fever caused by Salmonella enterica serovar Typhimurium are used. To study the interaction mechanism between bacteria and eukaryotic cells, one commonly uses cell lines, primary cells, and animal models. Within the host, bacteria can be located in various organs where they are exposed to different cell types, ranging from epithelial cells at the mucosal linings to phagocytic white blood cells. In each site, bacteria are exposed to specific sets of innate immune defense mechanisms, and to survive these threats, bacteria must rapidly adapt their gene expression profile to maximize their chance of survival in any situation. The rapid development of fluorescent reporter proteins and advances in microscopy-based techniques have provided new and promising approaches not only to locate bacteria in tissues, but also to analyze expression of virulence factors in individual bacteria and host cells during the progression of disease. These techniques enable, for the first time, studies of the complex microenvironments within infected organs and will reveal the alterations of bacterial physiology that occur during bacterial growth within a host.

Mechanisms of renal damage owing to infection

Urinary tract infection (UTI) is a common bacterial illness in children. It is known to be associated with an increased risk of permanent renal cell damage and scarring which may lead to generation of pathological conditions such as hypertension, pre-eclampsia during pregnancy, renal insufficiency, and end-stage kidney disease. The pathophysiology of renal scarring is still obscure, which makes the prevention of renal damage difficult. During acute infection, there are numerous factors that may contribute to tissue damage. Inflammatory responses are activated by host defense mechanisms as well as by specific bacterial virulence factors. Understanding of these complex mechanisms would be helpful to better identify children at high risk of developing renal scarring following UTI.

THE ACUTE INFLAMMATORY RESPONSE IN DIVERSE SHOCK STATES

A poorly controlled acute inflammatory response can lead to organ dysfunction and death. Severe systemic inflammation can be induced and perpetuated by diverse insults such as the administration of toxic bacterial products (e.g., endotoxin), traumatic injury, and hemorrhage. Here, we probe whether these varied shock states can be explained by a universal inflammatory system that is initiated through different means and, once initiated, follows a course specified by the cellular and molecular mechanisms of the immune and endocrine systems. To examine this question, we developed a mathematical model incorporating major elements of the acute inflammatory response in C57Bl/6 mice, using input from experimental data. We found that a single model with different initiators including the autonomic system could describe the response to various insults. This model was able to predict a dose range of endotoxin at which mice would die despite having been calibrated only in nonlethal inflammatory paradigms. These results show that the complex biology of inflammation can be modeled and supports the hypothesis that shock states induced by a range of physiologic challenges could arise from a universal response that is differently initiated and modulated.

Acute exposure to ethanol affects Toll-like receptor signaling and subsequent responses: an overview of recent studies

Ethanol suppresses innate resistance to a variety of microbes, and findings of studies from both our laboratory and other laboratories indicate suppression of responses is mediated through two Toll-like receptors (TLRs): TLR3 and TLR4. In this article, we review recent findings from studies in our laboratory, indicating that ethanol also suppresses responses mediated through other TLRs. Considering the importance of TLR-mediated responses in innate immunity, this supports the possibility that suppression of these responses may constitute a major mechanism by which ethanol suppresses innate immunity. In addition, ethanol-induced changes in cellular signaling and in patterns of gene expression induced through TLR3 were examined in mouse peritoneal macrophages, and these results are reviewed in this article. Signaling through TLR3 was inhibited, and results of DNA microarray analysis supported the notion that inhibition of an interferon-related amplification loop might be responsible for suppression of gene expression for several effector molecules of innate immunity and inflammation not previously known to be altered by ethanol. Thus, ethanol alters responses through most or all mouse TLRs, and this suppresses expression of a wide range of innate immune mediators.

Immunomodulatory clarithromycin treatment of experimental sepsis and acute pyelonephritis caused by multidrug-resistant Pseudomonas aeruginosa

Clarithromycin was administered intravenously to 55 rabbits to evaluate its effect on experimental sepsis caused by multidrug-resistant Pseudomonas aeruginosa. Acute pyelonephritis was induced after ligation of the right ureter and injection of 10(8) CFU of the test isolate per kg of body weight into the renal pelvis. The animals were divided into six groups: group A, controls; group B, rabbits that received one intravenous dose of 80 mg of clarithromycin per kg concomitantly with bacterial challenge; group C, rabbits that received two doses of clarithromycin, the second one of which was given 2 h after the first one; group D, rabbits that received 15 mg of amikacin per kg; group E, rabbits that received one dose of clarithromycin and amikacin; and group F, rabbits that received two doses of clarithromycin and amikacin. Serum endotoxin levels were estimated by the QCL-1000 Limulus amoebocyte lysate assay, tumor necrosis factor alpha (TNF-alpha) levels were measured by a bioassay, and malondialdehyde (MDA) levels were measured by the thiobarbiturate assay. Viable bacterial counts in various tissue samples were also assessed. The mean survival times of the animals in groups A, B, C, D, E, and F were 4.50, 7.69, 4.07, 4.55, 11.55, and 11.60 days, respectively (P = 0.033 for group D versus group F, P = 0.006 for group D versus group E, P = not significant for group B versus group E, P = 0.042 for group C versus group F). Serum endotoxin levels were similar between groups at all sampling times; TNF-alpha and MDA levels in groups B, C, E, and F decreased significantly over follow-up. The numbers of viable bacterial cells in the infected kidney were similar among the groups; those in the liver, spleen, lungs, and mesenteral lymph nodes were significantly decreased in groups B, E, and F compared to those in groups A and D. It is concluded that a prolongation of survival in animals with experimental sepsis caused by multidrug-resistant P. aeruginosa was achieved after coadministration of clarithromycin and amikacin and that the increased survival was probably attributable to the immunomodulatory properties of clarithromycin.

Cytokines and Cell Adhesion Molecules in the Inflammatory Response during Acute Pyelonephritis

Urinary tract infection is a common bacterial infection of childhood. Renal parenchymal scarring, a recognised complication of urinary tract infection, is responsible for up to 24% of children entering end-stage renal failure. Why acute inflammation results in renal scarring in some children whilst in others complete resolution occurs without scarring is at present poorly understood. This article reviews the role of the cytokines, adhesion molecules and growth factors in the inflammatory response during acute pyelonephritis and renal parenchymal scarring. We hypothesize that inter-individual variability in cellular response may in part be responsible for this variable clinical outcome.

Developmental aspects of Escherichia coli-induced innate responses in rat renal epithelial cells

Renal scarring after pyelonephritis is common in infancy. In this experimental study performed on tissue from 10-d-old infant and 40-d-old pubertal rats, several aspects of the renal innate immune response to a pyelonephritogenic strain of alpha-hemolysin-expressing Escherichia coli were compared. The kidney typically responds to urinary tract infection with release of proinflammatory cytokines, e.g. IL-6. Basal production of IL-6 from 10-d-old renal cortical tissue was approximately 20% of that from 40-d-old tissue. Six-hour incubation in the presence of supernatant from the E. coli culture caused an approximately 15-fold increase of IL-6 release in 10-d-old tissue and a 5-fold increase in 40-d-old tissue. The absolute level of IL-6 release in stimulated tissue was, however, significantly lower at 10 d than at 40 d. Lipopolysaccharide, the most immunogenic component of E. coli, signals via Toll-like receptor 4. Reverse transcriptase PCR performed on outer renal cortex indicated that expression of Toll-like receptor 4 mRNA was similar in both ages. Microdissection studies revealed that Toll-like receptor 4 mRNA was expressed in proximal tubules but not in glomeruli. The exotoxin alpha-hemolysin, expressed by a majority of uropathogenic E. coli isolates, stimulates IL-6 release via an alternative pathway that signals via intracellular calcium oscillations. We conclude that the higher susceptibility to pyelonephritic scarring is unlikely related to immaturity of innate immune system, as measured by cellular release of IL-6. Instead, the underlying mechanisms for pyelonephritic scarring are most likely multifactorial and may be mainly attributed to anatomic immaturity of the urinary tract.

Enhanced chemokine response in experimental acute Escherichia coli pyelonephritis in IL-1beta-deficient mice

The aim of the present study was to investigate the effects of IL-1beta and Escherichia coli on the expression and secretion of MIP-2, the mouse equivalent to human IL-8, MCP-1 and RANTES in the kidneys of mice with acute pyelonephritis. Female Bki NMRI, as well as IL-1beta deficient mice and their wild-type littermates, were transurethrally infected with either E. coli CFT 073 or injected with NaCl 0.9% (w/v) and thereafter obstructed for 6 h. The Bki NMRI mice were killed at 0, 24, 48 h and 6 days and the IL-1beta-deficient mice at 48 h. Chemokine mRNA and protein levels peaked at 24 h for the tested chemokines with the mRNA expression localized in the tubular epithelial cells and for MIP-2 also in neutrophils. Obstruction per se, also induced a chemokine expression similar to E. coli infection although at a lower level. Interestingly, MIP-2 levels were higher in the IL-1beta deficient mice as compared with the wild-type littermates. Likewise, the inflammatory changes were more frequent and, when present, more widespread in the IL-1beta-deficient mice than in the wild-type mice. Stimulation of a human renal tubular epithelial cell line (HREC), A498 and of primary human mesangial cells (HMC) with the same bacterial antigen depicted gene expression of the same chemokines. A rapid release of IL-8 and MCP-1 was observed from both cell types. RANTES response was delayed both in the HREC and the HMC. We conclude that acute E. coli pyelonephritis induces a MIP-2/IL-8, MCP-1 and RANTES expression and secretion localized primarily to the epithelial cells and that this production is confirmed after in vitro stimulation with the same bacterial antigen of human epithelial and mesangial cells. Blockade of induction of chemokine response may thus be an attractive target for possible therapeutic intervention.

Dual effects of Escherichia coli alpha-hemolysin on rat renal proximal tubule cells

BACKGROUND

alpha-Hemolysin (HlyA) producing Escherichia coli is a common cause of pyelonephritis and subsequent renal scarring. Recent studies have suggested that toxin secreted from HlyA E. coli may not only have a lytic effect, but also may activate a calcium signaling pathway in renal tubule cells. A dose dependent study was performed on the interaction between HlyA E. coli secretions and rat renal proximal tubule (PT) cells with regards to calcium signaling and cell morphology. The site of interaction between HlyA secretion and PT cells was examined by using an antagonist to a common binding motif in bacterial proteins.

METHODS

Supernatant from an overnight culture of HlyA was freshly prepared for each experiment. Renal PT cells from infant rats were cultured for three days and exposed for 30 minutes to four hours to supernatant or purified HlyA. Effects on cell morphology were studied semiquantitatively with light microscopy. Intracellular calcium was measured ratiometrically in the presence or absence of drugs.

RESULTS

Renal PT cells incubated with low doses of HlyA supernatant responded within five minutes with calcium oscillations. Morphology appeared unchanged after four hours of incubation. In contrast, high doses of HlyA caused a sustained increase in intracellular calcium and majority of cells were lysed within four hours. Calcium oscillations caused by lower doses of HlyA supernatant were highly regular and slow in the 10 to 12 minute range. Oscillations were abolished by 6-cyano-7-nitroquinoxaline-2, 3-dione (CNQX), indicating that HlyA is interacting with a QPB/LAOBP-motif.

CONCLUSION

HlyA secreted from uropathogenic E. coli exerts a dual action on renal PT cells. Sublytical concentrations induce a response that may serve as a host defense, while high concentrations cause irreversible cell damage. The data emphasize the importance of high diuresis in urinary tract infection.

Cytokine Polymorphisms and Susceptibility to Severe Infectious Diseases

Cytokines are key regulators of the host response to infection, controlling the inflammatory reaction which is an essential component of the defense mechanisms. The major importance of these proteins in the pathogenesis and outcome of infectious diseases has been clearly demonstrated. In humans, there is increasing evidence that the host's cytokine response is genetically determined and that the genetic variability of cytokines underlies the complexity of interindividual differences in the immune response to micro organism invasions. We review the influence of host cytokine gene on the susceptibility to and the severity of parasitic, bacterial and viral infections. Proinflammatory cytokine polymorphisms are discussed in detail because of their importance in the course of severe infections such as meningococcal disease, cerebral malaria and septic shock. Genetic variants of the IL-10 gene, an antiinflammatory cytokine appear to be responsible for an uncontrolled and intense CARS and may have also dramatic consequences as an overwhelming inflammatory response. Our greater understanding of the genetic factors that influence mortality and morbidity of infectious diseases will permit identification of genomic markers which may be required for risk stratification of patients targeted for novel immunomodulatory treatments helping clinicians to select the most appropriate treatment options for their patients.