Insulin receptor orchestrates kidney antibacterial defenses.

Urinary tract infection (UTI) commonly afflicts people with diabetes. This augmented infection risk is partly due to deregulated insulin receptor (IR) signaling in the kidney collecting duct. The collecting duct is composed of intercalated cells (ICs) and principal cells (PCs). Evidence suggests that ICs contribute to UTI defenses. Here, we interrogate how IR deletion in ICs impacts antibacterial defenses against uropathogenic Escherichia coli. We also explore how IR deletion affects immune responses in neighboring PCs with intact IR expression. To accomplish this objective, we profile the transcriptomes of IC and PC populations enriched from kidneys of wild-type and IC-specific IR knock-out mice that have increased UTI susceptibility. Transcriptomic analysis demonstrates that IR deletion suppresses IC-integrated stress responses and innate immune defenses. To define how IR shapes these immune defenses, we employ murine and human kidney cultures. When challenged with bacteria, murine ICs and human kidney cells with deregulated IR signaling cannot engage central components of the integrated stress response-including activating transcriptional factor 4 (ATF4). Silencing ATF4 impairs NFkB activation and promotes infection. In turn, NFkB silencing augments infection and suppresses antimicrobial peptide expression. In diabetic mice and people with diabetes, collecting duct cells show reduced IR expression, impaired integrated stress response engagement, and compromised immunity. Collectively, these translational data illustrate how IR orchestrates collecting duct antibacterial responses and the communication between ICs and PCs.

Repurposing HDAC inhibitors to enhance ribonuclease 4 and 7 expression and reduce urinary tract infection.

With the emergence of antibiotic-resistant bacteria, innovative approaches are needed for the treatment of urinary tract infections. Boosting antimicrobial peptide expression may provide an alternative to antibiotics. Here, we developed reporter cell lines and performed a high-throughput screen of clinically used drugs to identify compounds that boost ribonuclease 4 and 7 expression (RNase 4 and 7), peptides that have antimicrobial activity against antibiotic-resistant uropathogens. This screen identified histone deacetylase (HDAC) inhibitors as effective RNase 4 and RNase 7 inducers. Validation studies in primary human kidney and bladder cells confirmed pan-HDAC inhibitors as well as the HDAC class I inhibitor, MS-275, induce RNase 4 and RNase 7 to protect human kidney and bladder cells from uropathogenic Escherichia coli. When we administered MS-275 to mice, RNase 4 and 7 expression increased and mice were protected from acute transurethral E. coli challenge. In support of this mechanism, MS-275 treatment increased acetylated histone H3 binding to the RNASE4 and RNASE7 promoters. Overexpression and knockdown of HDAC class I proteins identified HDAC3 as a primary regulator of RNase 4 and 7. These results demonstrate the protective effects of enhancing RNase 4 and RNase 7, opening the door to repurposing medications as antibiotic conserving therapeutics for urinary tract infection.

Analysing the influence of dapagliflozin on urinary tract infection vulnerability and kidney injury in mice infected with uropathogenic Escherichia coli.

AIM: Sodium-glucose co-transporter-2 (SGLT2) inhibitors have revolutionized clinical medicine, but their association with urinary tract infection (UTI) risk remains debated. This study investigates the influence of dapagliflozin on UTI outcomes, focusing on kidney injury. MATERIALS AND METHODS: Female non-diabetic C57BL/6J and C3H/HeOuJ mice, along with diabetic db/db mice, were orally administered dapagliflozin (1 mg/kg or 10 mg/kg) for 7 days before transurethral uropathogenic Escherichia coli (UPEC) infection. Mice were killed either 24 h after UTI or after six additional days of dapagliflozin treatment. UPEC titers were enumerated, and kidney histopathology, injury, fibrosis and function were assessed. RESULTS: Vehicle- and dapagliflozin-treated C57BL/6J mice exhibited similar urine and bladder UPEC titers, with minimal kidney burden 24 h after UTI. In C3H/HeOuJ mice, UPEC burden was comparable in vehicle- and 1 mg/kg dapagliflozin-treated groups both 24 h and 7 days after UTI. However, C3H/HeOuJ mice receiving 10 mg/kg dapagliflozin had increased UPEC titers in the urine, bladder and kidneys at both endpoints. Kidney injury and fibrosis markers, as well as kidney function, were similar in vehicle and dapagliflozin groups. In diabetic db/db mice receiving dapagliflozin, UPEC strain UTI89 titers were reduced 7 days after UTI compared to vehicle-treated mice, but no difference in UPEC titers was observed when mice were infected with UPEC strain CFT073. Kidney injury and fibrosis markers and kidney function remained similar across treatment groups. CONCLUSIONS: Dapagliflozin does not consistently influence UTI susceptibility and shows limited impact on kidney injury or fibrosis, suggesting SGLT2 inhibitors have minimal effects on UTI-related kidney complications.

Biomarkers for urinary tract infection: present and future perspectives.

A prompt diagnosis of urinary tract infection (UTI) is necessary to minimize its symptoms and limit sequelae. The current UTI screening by urine test strip analysis and microscopic examination has suboptimal diagnostic accuracy. A definitive diagnosis of UTI by urine culture takes two to three days for the results. These limitations necessitate a need for better biomarkers for the diagnosis and subsequent management of UTI in children. Here, we review the value of currently available UTI biomarkers and highlight the potential of emerging biomarkers that can facilitate a more rapid and accurate UTI diagnosis. Of the newer UTI biomarkers, the most promising are blood procalcitonin (PCT) and urinary neutrophil gelatinase-associated lipocalin (NGAL). PCT can provide diagnostic benefits and should be considered in patients who have a blood test for other reasons. NGAL, which is on the threshold of clinical care, needs more research to address its scope and utilization, including point-of-care application. Employment of these and other biomarkers may ultimately improve UTI diagnosis, guide UTI therapy, reduce antibiotic use, and mitigate UTI complications.

Chondronecrosis of the cricoid treated with hyperbaric oxygen therapy: A case series.

We present two cases of cricoid chondronecrosis treated with hyperbaric oxygen (HBO2) therapy. Both patients presented with biphasic stridor and dyspnea several weeks after an intubation event. Tracheostomy was ultimately performed for airway protection, followed by antibiotic treatment and outpatient HBO2 therapy. Both patients were decannulated within six months of presentation and after at least 20 HBO2 therapy sessions. Despite a small sample size, our findings are consistent with data supporting HBO2 therapy's effects on tissue edema, neovascularization, and HBO2 potentiation of antibiotic treatment and leukocyte function. We suggest HBO2 therapy may have accelerated airway decannulation by way of infection resolution as well as the revitalization of upper airway tissues, ultimately renewing the structural integrity of the larynx. When presented with this rare but significant clinical challenge, physicians should be aware of the potential benefits of HBO2 therapy.

Urinary Tract Infections in Children.

Despite the American Academy of Pediatrics guidelines for the evaluation, treatment, and management of urinary tract infections (UTIs), UTI diagnosis and management remains challenging for clinicians. Challenges with acute UTI management stem from vague presenting signs and symptoms, diagnostic uncertainty, limitations in laboratory testing, and selecting appropriate antibiotic therapy in an era with increasing rates of antibiotic-resistant uropathogens. Recurrent UTI management remains difficult due to an incomplete understanding of the factors contributing to UTI, when to assess a child with repeated infections for kidney and urinary tract anomalies, and limited prevention strategies. To help reduce these uncertainties, this review provides a comprehensive overview of UTI epidemiology, risk factors, diagnosis, treatment, and prevention strategies that may help pediatricians overcome the challenges associated with acute and recurrent UTI management.

Neutrophil-Macrophage Imbalance Drives the Development of Renal Scarring during Experimental Pyelonephritis.

BACKGROUND: In children, the acute pyelonephritis that can result from urinary tract infections (UTIs), which commonly ascend from the bladder to the kidney, is a growing concern because it poses a risk of renal scarring and irreversible loss of kidney function. To date, the cellular mechanisms underlying acute pyelonephritis-driven renal scarring remain unknown. METHODS: We used a preclinical model of uropathogenic Escherichia coli-induced acute pyelonephritis to determine the contribution of neutrophils and monocytes to resolution of the condition and the subsequent development of kidney fibrosis. We used cell-specific monoclonal antibodies to eliminate neutrophils, monocytes, or both. Bacterial ascent and the cell dynamics of phagocytic cells were assessed by biophotonic imaging and flow cytometry, respectively. We used quantitative RT-PCR and histopathologic analyses to evaluate inflammation and renal scarring. RESULTS: We found that neutrophils are critical to control bacterial ascent, which is in line with previous studies suggesting a protective role for neutrophils during a UTI, whereas monocyte-derived macrophages orchestrate a strong, but ineffective, inflammatory response against uropathogenic, E. coli-induced, acute pyelonephritis. Experimental neutropenia during acute pyelonephritis resulted in a compensatory increase in the number of monocytes and heightened macrophage-dependent inflammation in the kidney. Exacerbated macrophage-mediated inflammatory responses promoted renal scarring and compromised renal function, as indicated by elevated serum creatinine, BUN, and potassium. CONCLUSIONS: These findings reveal a previously unappreciated outcome for neutrophil-macrophage imbalance in promoting host susceptibility to acute pyelonephritis and the development of permanent renal damage. This suggests targeting dysregulated macrophage responses might be a therapeutic tool to prevent renal scarring during acute pyelonephritis.

Expression and function of human ribonuclease 4 in the kidney and urinary tract.

Antimicrobial peptides are essential host defense mechanisms that prevent urinary tract infections. Recent studies have demonstrated that peptides in the ribonuclease A superfamily have antimicrobial activity against uropathogens and protect the urinary tract from uropathogenic Escherichia coli (UPEC). Little is known about the antibacterial function or expression of ribonuclease 4 (RNase 4) in the human urinary tract. Here, we show that full-length recombinant RNase 4 peptide and synthetic amino-terminal RNase 4 peptide fragment have antibacterial activity against UPEC and multidrug-resistant (MDR)-UPEC. RNASE4 transcript expression was detected in human kidney and bladder tissue using quantitative real-time PCR. Immunostaining or in situ hybridization localized RNase 4 expression to proximal tubules, principal and intercalated cells in the kidney's collecting duct, and the bladder urothelium. Urinary RNase 4 concentrations were quantified in healthy controls and females with a history of urinary tract infection. Compared with controls, urinary RNase 4 concentrations were significantly lower in females with a history of urinary tract infection. When RNase 4 was neutralized in human urine or silenced in vitro using siRNA, urinary UPEC replication or attachment to and invasion of urothelial and kidney medullary cells increased. These data show that RNase 4 has antibacterial activity against UPEC, is expressed in the human urinary tract, and can contribute to host defense against urinary tract infections.NEW & NOTEWORTHY Ribonuclease 4 (RNase 4) is a newly identified host defense peptide in the human kidney and bladder. RNase 4 kills uropathogenic Escherichia coli (UPEC) and multidrug-resistant UPEC. RNase 4 prevents invasive UPEC infection and suppressed RNase 4 expression may be a risk factor for more severe or recurrent urinary tract infection.

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.

Ribonuclease 7 Shields the Kidney and Bladder from Invasive Uropathogenic Escherichia coli Infection.

BACKGROUND: Evidence suggests that antimicrobial peptides, components of the innate immune response, protect the kidneys and bladder from bacterial challenge. We previously identified ribonuclease 7 (RNase 7) as a human antimicrobial peptide that has bactericidal activity against uropathogenic Escherichia coli (UPEC). Functional studies assessing RNase 7's contributions to urinary tract defense are limited. METHODS: To investigate RNase 7's role in preventing urinary tract infection (UTI), we quantified urinary RNase 7 concentrations in 29 girls and adolescents with a UTI history and 29 healthy female human controls. To assess RNase 7's antimicrobial activity in vitro in human urothelial cells, we used siRNA to silence urothelial RNase 7 production and retroviral constructs to stably overexpress RNase 7; we then evaluated UPEC's ability to bind and invade these cells. For RNase 7 in vivo studies, we developed humanized RNase 7 transgenic mice, subjected them to experimental UTI, and enumerated UPEC burden in the urine, bladder, and kidneys. RESULTS: Compared with controls, study participants with a UTI history had 1.5-fold lower urinary RNase 7 concentrations. When RNase 7 was silenced in vitro, the percentage of UPEC binding or invading human urothelial cells increased; when cells overexpressed RNase 7, UPEC attachment and invasion decreased. In the transgenic mice, we detected RNase 7 expression in the kidney's intercalated cells and bladder urothelium. RNase 7 humanized mice exhibited marked protection from UPEC. CONCLUSIONS: These findings provide evidence that RNase 7 has a role in kidney and bladder host defense against UPEC and establish a foundation for investigating RNase 7 as a UTI prognostic marker or nonantibiotic-based therapy.

The burden of common infections in children and adolescents with diabetes mellitus: A Pediatric Health Information System study.

BACKGROUND: People with diabetes mellitus (DM) have increased infection risk. The healthcare utilization of pediatric and adolescent diabetic patients with infection is not well defined. This study evaluates the number of pediatric and adolescent patients with DM that seek medical treatment for infection management and assesses its socioeconomic impact. METHODS: A retrospective analysis was performed using the Pediatric Health Information System (PHIS) database on children and adolescents with DM who presented to the Emergency Department (ED) or were hospitalized for infection management from 2008 to 2014. The PHIS database collects admission, demographic, and economic data from 44 freestanding children's hospitals across the United States. RESULTS: In total, 123 599 diabetic patient encounters were identified (77% type 1 DM, 23% type 2 DM). ED visits and hospitalizations for type 1 DM and type 2 DM increased throughout the study period. Total charges for these encounters were greater than $250 million dollars per year and increased each year. Infection encounters make up more than 30% of that cost while accounting for only 14% of the visits. Respiratory infections were the most common type of infection followed by skin and soft tissue infections for both ED care and inpatient hospitalizations. Patients with infections had longer hospital length of stay and higher cost per day than those without infections. CONCLUSIONS: Children and adolescents with type 1 and type 2 DM commonly present to the ED and require hospitalization for infection evaluation and management. Encounters with infection make up a large proportion of a growing economic burden on the United States' healthcare system. As the prevalence of DM grows, this burden can be expected to become even more significant. Cost-effective strategies for the prevention of infection in pediatric patients with DM are needed.

Urinary Tract Infection and Antimicrobial Stewardship in the Emergency Department.

OBJECTIVES: The aims of this study were to assess empiric antibiotic use for presumed urinary tract infection (UTI) in the emergency department (ED) and to determine how often urine culture results subsequently do not confirm the diagnosis. METHODS: This study is a retrospective cohort study of patients aged 21 years or younger in the Nationwide Children's Hospital ED from May 1, 2012, to October 31, 2012, who had a urinalysis and urine culture performed and were discharged home with empiric antibiotic therapy for presumed UTI. Patients with known urinary tract anomaly or antibiotic use in the previous 7 days were excluded. Confirmed UTI was defined as pyuria (>5 white blood cells per high-power field or dipstick positive for leukocyte esterase) and a positive urine culture (≥50,000 colony-forming units/mL of a uropathogen). RESULTS: Of the 175 enrolled patients, urine was obtained by clean catch in 138 (79%), catheterization in 35 (20%), first-pass void in 1 (0.6%), and undocumented method in 1 (0.6%). Pyuria was demonstrated in 164 patients (94%), but only 97 (55%) had a positive urine culture. The combination of pyuria and a positive urine culture confirmed UTI in 90 patients (51%). The most commonly prescribed antibiotics were cefdinir in 103 patients (59%), trimethoprim/sulfamethoxazole in 40 (23%), and ciprofloxacin in 23 (13%). The median duration of prescribed therapy was 10 days (interquartile range, 7-10 days). Treatment duration was correlated negatively with age (r = -0.53, P < 0.01). CONCLUSIONS: The current management of suspected UTI in ED patients results in unnecessary antibiotic exposure, highlighting an important opportunity for outpatient antimicrobial stewardship efforts.

Inflammation drives renal scarring in experimental pyelonephritis.

Acquired renal scarring occurs in a subset of patients following febrile urinary tract infections and is associated with hypertension, proteinuria, and chronic kidney disease. Limited knowledge of histopathology, immune cell recruitment, and gene expression changes during pyelonephritis restricts the development of therapies to limit renal scarring. Here, we address this knowledge gap using immunocompetent mice with vesicoureteral reflux. Transurethral inoculation of uropathogenic Escherichia coli in C3H/HeOuJ mice leads to renal mucosal injury, tubulointerstitial nephritis, and cortical fibrosis. The extent of fibrosis correlates most significantly with inflammation at 7 and 28 days postinfection. The recruitment of neutrophils and inflammatory macrophages to infected kidneys is proportional to renal bacterial burden. Transcriptome analysis reveals molecular signatures associated with renal ischemia-reperfusion injury, immune cell chemotaxis, and leukocyte activation. This murine model recapitulates the cardinal histopathological features observed in humans with acquired renal scarring following pyelonephritis. The integration of histopathology, quantification of cellular immune influx, and unbiased transcriptional profiling begins to define potential mechanisms of tissue injury during pyelonephritis in the context of an intact immune response. The clear relationship between inflammatory cell recruitment and fibrosis supports the hypothesis that acquired renal scarring arises as a consequence of excessive host inflammation and suggests that immunomodulatory therapies should be investigated to reduce renal scarring in patients with pyelonephritis.

Insulin and the phosphatidylinositol 3-kinase signaling pathway regulate Ribonuclease 7 expression in the human urinary tract.

Diabetes mellitus is a systemic disease associated with a deficiency of insulin production or action. Diabetic patients have an increased susceptibility to infection with the urinary tract being the most common site. Recent studies suggest that Ribonuclease 7 (RNase 7) is a potent antimicrobial peptide that plays an important role in protecting the urinary tract from bacterial insult. Because the impact of diabetes on RNase 7 expression and function are unknown, we investigated the effects of insulin on RNase 7 using human urine specimens. The urinary RNase 7 concentrations were measured in healthy control patients and insulin-deficient type 1 diabetics before and after starting insulin therapy. Compared with controls, diabetic patients had suppressed urinary RNase 7 concentrations, which increased with insulin. Using primary human urothelial cells, the mechanisms by which insulin stimulates RNase 7 synthesis were next explored. Insulin induced RNase 7 production via the phosphatidylinositide 3-kinase signaling pathway (PI3K/AKT) to shield urothelial cells from uropathogenic E. coli. In contrast, uropathogenic E. coli suppressed PI3K/AKT activity and RNase 7 production. Thus, insulin and PI3K/AKT signaling are essential for RNase 7 expression and increased infection risks in diabetic patients may be secondary to suppressed RNase 7 production. Our data may provide unique insight into novel urinary tract infection therapeutic strategies in at-risk populations.

Evaluation of novel urinary tract infection biomarkers in children.

BACKGROUND: Pediatricians frequently use urinalysis to diagnose urinary tract infection (UTI) while awaiting urine culture results, but sensitivity and specificity of urinalysis are limited. This study evaluated the diagnostic accuracy of the antimicrobial peptides (AMPs) human α-defensin 5 (HD5) and human neutrophil peptides (HNP) 1-3 as novel UTI biomarkers in children. METHODS: We prospectively enrolled 199 pediatric Emergency Department or Urgent Care patients evaluated for a UTI. Urine concentrations of HD5 and HNP1-3 were measured by enzyme-linked immunosorbent assay. Urine culture was the reference standard. Sensitivities and specificities of leukocyte esterase (LE), HD5, HNP1-3, and test combinations were compared. RESULTS: For predicting positive urine culture, the areas under the receiver-operating characteristic curves for HD5 and HNP1-3 were 0.86 (95% confidence interval (CI): 0.81-0.92) and 0.88 (95% CI: 0.82-0.93), respectively. Compared to LE ≥ trace, the combination test "LE and HD5" increased specificity by 6% (95% CI: 3-10%) without decreasing sensitivity. In the subgroup whose urine was collected by a clean-catch method, combination tests "LE and HD5" and "HD5 and HNP1-3" increased specificity by > 10% compared to LE alone. CONCLUSION: Urine AMP profiles are a promising novel strategy as an adjunct to urinalysis to aid UTI diagnosis in children.

A Review of Ribonuclease 7's Structure, Regulation, and Contributions to Host Defense.

The Ribonuclease A Superfamily is composed of a group of structurally similar peptides that are secreted by immune cells and epithelial tissues. Several members of the Ribonuclease A Superfamily demonstrate antimicrobial activity, and it has been suggested that some of these ribonucleases play an essential role in host defense. Ribonuclease 7 (RNase 7) is an epithelial-derived secreted peptide with potent broad-spectrum antimicrobial activity. This review summarizes the published literature on RNase 7's antimicrobial properties, structure, regulation, and contributions to host defense. In doing so, we conclude by highlighting key knowledge gaps that must be investigated to completely understand the potential of developing RNase 7 as a novel therapeutic for human infectious diseases.

The innate immune response during urinary tract infection and pyelonephritis.

Despite its proximity to the fecal flora, the urinary tract is considered sterile. The precise mechanisms by which the urinary tract maintains sterility are not well understood. Host immune responses are critically important in the antimicrobial defense of the urinary tract. During recent years, considerable advances have been made in our understanding of the mechanisms underlying immune homeostasis of the kidney and urinary tract. Dysfunctions in these immune mechanisms may result in acute disease, tissue destruction and overwhelming infection. The objective of this review is to provide an overview of the innate immune response in the urinary tract in response to microbial assault. In doing so, we focus on the role of antimicrobial peptides-a ubiquitous component of the innate immune response.

Current and emerging strategies to curb antibiotic-resistant urinary tract infections.

Rising rates of antibiotic resistance in uropathogenic bacteria compromise patient outcomes and prolong hospital stays. Consequently, new strategies are needed to prevent and control the spread of antibiotic resistance in uropathogenic bacteria. Over the past two decades, sizeable clinical efforts and research advances have changed urinary tract infection (UTI) treatment and prevention strategies to conserve antibiotic use. The emergence of antimicrobial stewardship, policies from national societies, and the development of new antimicrobials have shaped modern UTI practices. Future UTI management practices could be driven by the evolution of antimicrobial stewardship, improved and readily available diagnostics, and an improved understanding of how the microbiome affects UTI. Forthcoming UTI treatment and prevention strategies could employ novel bactericidal compounds, combinations of new and classic antimicrobials that enhance bacterial killing, medications that prevent bacterial attachment to uroepithelial cells, repurposing drugs, and vaccines to curtail the rising rates of antibiotic resistance in uropathogenic bacteria and improve outcomes in people with UTI.

Insulin receptor signaling engages bladder urothelial defenses that limit urinary tract infection.

Urinary tract infections (UTIs) commonly afflict people with diabetes. To better understand the mechanisms that predispose diabetics to UTIs, we employ diabetic mouse models and altered insulin signaling to show that insulin receptor (IR) shapes UTI defenses. Our findings are validated in human biosamples. We report that diabetic mice have suppressed IR expression and are more susceptible to UTIs caused by uropathogenic Escherichia coli (UPEC). Systemic IR inhibition increases UPEC susceptibility, while IR activation reduces UTIs. Localized IR deletion in bladder urothelium promotes UTI by increasing barrier permeability and suppressing antimicrobial peptides. Mechanistically, IR deletion reduces nuclear factor κB (NF-κB)-dependent programming that co-regulates urothelial tight junction integrity and antimicrobial peptides. Exfoliated urothelial cells or urine samples from diabetic youths show suppressed expression of IR, barrier genes, and antimicrobial peptides. These observations demonstrate that urothelial insulin signaling has a role in UTI prevention and link IR to urothelial barrier maintenance and antimicrobial peptide expression.

Murine Ribonuclease 6 Limits Bacterial Dissemination during Experimental Urinary Tract Infection.

INTRODUCTION: The ribonuclease (RNase) A superfamily encodes cationic antimicrobial proteins with potent microbicidal activity toward uropathogenic bacteria. Ribonuclease 6 (RNase6) is an evolutionarily conserved, leukocyte-derived antimicrobial peptide with potent microbicidal activity toward uropathogenic Escherichia coli (UPEC), the most common cause of bacterial urinary tract infections (UTIs). In this study, we generated Rnase6-deficient mice to investigate the hypothesis that endogenous RNase 6 limits host susceptibility to UTI. METHODS: We generated a Rnase6EGFP knock-in allele to identify cellular sources of Rnase6 and determine the consequences of homozygous Rnase6 deletion on antimicrobial activity and UTI susceptibility. RESULTS: We identified monocytes and macrophages as the primary cellular sources of Rnase6 in bladders and kidneys of Rnase6EGFP/+ mice. Rnase6 deficiency (i.e., Rnase6EGFP/EGFP) resulted in increased upper urinary tract UPEC burden during experimental UTI, compared to Rnase6+/+ controls. UPEC displayed increased intracellular survival in Rnase6-deficient macrophages. CONCLUSION: Our findings establish that RNase6 prevents pyelonephritis by promoting intracellular UPEC killing in monocytes and macrophages and reinforce the overarching contributions of endogenous antimicrobial RNase A proteins to host UTI defense.