NRF2 promotes urothelial cell response to bacterial infection by regulating reactive oxygen species and RAB27B expression

Multi-step strategies for synergistic treatment of urinary tract infections based on D-xylose-decorated antimicrobial peptide carbon dots

Urinary tract infections (UTIs) caused by Uropathogenic Escherichia coli (UPEC), often reoccur due to the formation of intracellular bacterial colonies (IBCs) and antibiotic resistance. Given the significance of YadC for UPEC infection in our previous study, we developed D-xylose-decorated ɛ-poly-L-lysine (εPL)-based carbon dots (D-xyl@εPLCDs) that can be traced, and employed multi-step approaches to elucidate the functional roles of D-xyl@εPLCDs in UPEC infection. Compared to undecorated particles, D-xyl@εPLCDs demonstrate YadC-dependent bacterial targeting and exhibit enhanced bactericidal activities both intracellularly and extracellularly. Moreover, pre-treatment of D-xyl@εPLCDs before infection blocked the subsequent adhesion and invasion of UPEC to bladder epithelial cells 5637. Increase of ROS production and innate immune responses were observed in bladder epithelial cells 5637 treated with D-xyl@εPLCDs. In addition, treatment of D-xyl@εPLCDs post-infection facilitated clearance of UPEC in the bladders of the UTI mouse model, and reduced ultimate number of neutrophils, macrophages and inflammatory responses raised by invaded bacteria. Collectively, we presented a comprehensive evaluating system to show that D-xyl@εPLCDs exhibits superior bactericidal effects against UPEC, making them a promising candidate for drug development in clinical UTI therapeutics.

Mechanisms of oxidative stress in interstitial cystitis/bladder pain syndrome

Interstitial cystitis/bladder pain syndrome (IC/BPS) is characterized by bladder and/or pelvic pain, increased urinary urgency and frequency and nocturia. The pathophysiology of IC/BPS is poorly understood, and theories include chronic inflammation, autoimmune dysregulation, bacterial cystitis, urothelial dysfunction, deficiency of the glycosaminoglycan (GAG) barrier and urine cytotoxicity. Multiple treatment options exist, including behavioural interventions, oral medications, intravesical instillations and procedures such as hydrodistension; however, many clinical trials fail, and patients experience an unsatisfactory treatment response, likely owing to IC/BPS phenotype heterogeneity and the use of non-targeted interventions. Oxidative stress is implicated in the pathogenesis of IC/BPS as reactive oxygen species impair bladder function via their involvement in multiple molecular mechanisms. Kinase signalling pathways, nociceptive receptors, mast-cell activation, urothelial dysregulation and circadian rhythm disturbance have all been linked to reactive oxygen species and IC/BPS. However, further research is necessary to fully uncover the role of oxidative stress in the pathways driving IC/BPS pathogenesis. The development of new models in which these pathways can be manipulated will aid this research and enable further investigation of promising therapeutic targets.

Hormesis as an adaptive response to infection

Hormesis is a phenomenon whereby low-level stress can improve cellular, organ, or organismal fitness in response to a subsequent similar or other stress insult. Whereas hormesis is thought to contribute to the fitness benefits arising from symbiotic host-microbe interactions, the putative benefits of hormesis in host-pathogen interactions have yet to be explored. Hormetic responses have nonetheless been reported in experimental models of infection, a common feature of which is regulation of host mitochondrial function. We propose that these mitohormetic responses could be harnessed therapeutically to limit the severity of infectious diseases.

The role of Nrf2 signaling in parasitic diseases and its therapeutic potential

In response to invading parasites, one of the principal arms of innate immunity is oxidative stress, caused by reactive oxygen species (ROS). However, oxidative stresses play dual functions in the disease, whereby free radicals promote pathogen removal, but they can also trigger inflammation, resulting in tissue injuries. A growing body of evidence has strongly supported the notion that nuclear factor erythroid 2-related factor 2 (NRF) signaling is one of the main antioxidant pathways to combat this oxidative burst against parasites. Given the important role of NRF2 in oxidative stress, in this review, we investigate the activation mechanism of the NRF2 antioxidant pathway in different parasitic diseases, such as malaria, leishmaniasis, trypanosomiasis, toxoplasmosis, schistosomiasis, entamoebiasis, and trichinosis.

Epigenetic insights to pediatric uropathology: Celebrating the fundamental biology vision of Tony Khoury

INTRODUCTION

Many pediatric urology conditions affect putatively normal tissues or appear too commonly to be based solely on specific DNA mutations. Understanding epigenetic mechanisms in pediatric urology, therefore, has many implications that can impact cell and tissue responses to settings, such as environmental and hormonal influences on urethral development, uropathogenic infections, obstructive stimuli, all of which originate externally or extracellularly. Indeed, the cell's response to external stimuli is often mediated epigenetically. In this commentary, we highlight work on the critical role that epigenetic machinery, such as DNA methyltransferases (DNMTs), Enhancer of Zeste Polycomb Repressive Complex 2 Subunit (EZH2), and others play in regulating gene expression and cellular functions in three urological contexts.

DESIGN

Animal and cellular constructs were used to model clinical pediatric uropathology. The hypertrophy, trabeculation, and fibrosis of the chronically obstructed bladder was explored using smooth muscle cell models employing disorganised vs. normal extracellular matrix (ECM), as well as a new animal model of chronic obstructive bladder disease (COBD) which retains its pathologic features even after bladder de-obstruction. Cell models from human and murine hypospadias or genital tubercles (GT) were used to illustrate developmental responses and epigenetic dependency of key developmental genes. Finally, using bladder urothelial and organoid culture systems, we examined activity of epigenetic machinery in response to non uropathogenic vs. uropathogenic E.coli (UPEC). DNMT and EZH2 expression and function were interrogated in these model systems.

RESULTS

Disordered ECM exerted a principal mitogenic and epigenetic role for on bladder smooth muscle both in vitro and in CODB in vivo. Key genes, e.g., BDNF and KCNB2 were under epigenetic regulation in actively evolving obstruction and COBD, though each condition showed distinct epigenetic responses. In models of hypospadias, estrogen strongly dysregulated WNT and Hox expression, which was normalized by epigenetic inhibition. Finally, DNA methylation machinery in the urothelium showed specific activation when challenged by uropathogenic E.coli. Similarly, UPEC induces hypermethylation and downregulation of the growth suppressor p16INK4A. Moreover, host cells exposed to UPEC produced secreted factors inducing epigenetic responses transmissible from one affected cell to another without ongoing bacterial presence.

DISCUSSION

Microenvironmental influences altered epigenetic activity in the three described urologic contexts. Considering that many obstructed bladders continue to display abnormal architecture and dysfunction despite relief of obstruction similar to after resection of posterior valves or BPH, the epigenetic mechanisms described highlight novel approaches for understanding the underlying smooth muscle myopathy of this crucial clinical problem. Similarly, there is evidence for an epigenetic basis of xenoestrogen on development of hypospadias, and UTI-induced pan-urothelial alteration of epigenetic marks and propensity for subsequent (recurrent) UTI. The impact of mechanical, hormonal, infectious triggers on genitourinary epigenetic machinery activity invite novel avenues for targeting epigenetic modifications associated with these non-cancer diseases in urology. This includes the use of deactivated CRISPR-based technologies for precise epigenome targeting and editing. Overall, we underscore the importance of understanding epigenetic regulation in pediatric urology for the development of innovative therapeutic and management strategies.

Nucleoside-diphosphate kinase of uropathogenic Escherichia coli inhibits caspase-1-dependent pyroptosis facilitating urinary tract infection

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infection (UTI). UPEC invades bladder epithelial cells (BECs) via fusiform vesicles, escapes into the cytosol, and establishes biofilm-like intracellular bacterial communities (IBCs). Nucleoside-diphosphate kinase (NDK) is secreted by pathogenic bacteria to enhance virulence. However, whether NDK is involved in UPEC pathogenesis remains unclear. Here, we find that the lack of ndk impairs the colonization of UPEC CFT073 in mouse bladders and kidneys owing to the impaired ability of UPEC to form IBCs. Furthermore, we demonstrate that NDK inhibits caspase-1-dependent pyroptosis by consuming extracellular ATP, preventing superficial BEC exfoliation, and promoting IBC formation. UPEC utilizes the reactive oxygen species (ROS) sensor OxyR to indirectly activate the regulator integration host factor, which then directly activates ndk expression in response to intracellular ROS. Here, we reveal a signaling transduction pathway that UPEC employs to inhibit superficial BEC exfoliation, thus facilitating acute UTI.

Uropathogenic Escherichia coli infection: innate immune disorder, bladder damage, and Tailin Fang II

Background

Uropathogenic Escherichia coli (UPEC) activates innate immune response upon invading the urinary tract, whereas UPEC can also enter bladder epithelial cells (BECs) through interactions with fusiform vesicles on cell surfaces and subsequently escape from the vesicles into the cytoplasm to establish intracellular bacterial communities, finally evading the host immune system and leading to recurrent urinary tract infection (RUTI). Tailin Fang II (TLF-II) is a Chinese herbal formulation composed of botanicals that has been clinically proven to be effective in treating urinary tract infection (UTI). However, the underlying therapeutic mechanisms remain poorly understood.

Methods

Network pharmacology analysis of TLF-II was conducted. Female Balb/C mice were transurethrally inoculated with UPEC CFT073 strain to establish the UTI mouse model. Levofloxacin was used as a positive control. Mice were randomly divided into four groups: negative control, UTI, TLF-II, and levofloxacin. Histopathological changes in bladder tissues were assessed by evaluating the bladder organ index and performing hematoxylin-eosin staining. The bacterial load in the bladder tissue and urine sample of mice was quantified. Activation of the TLR4-NF-κB pathway was investigated through immunohistochemistry and western blotting. The urinary levels of interleukin (IL)-1β and IL-6 and urine leukocyte counts were monitored. We also determined the protein expressions of markers associated with fusiform vesicles, Rab27b and Galectin-3, and levels of the phosphate transporter protein SLC20A1. Subsequently, the co-localization of Rab27b and SLC20A1 with CFT073 was examined using confocal fluorescence microscopy.

Results

Data of network pharmacology analysis suggested that TLF-II could against UTI through multiple targets and pathways associated with innate immunity and inflammation. Additionally, TLF-II significantly attenuated UPEC-induced bladder injury and reduced the bladder bacterial load. Meanwhile, TLF-II inhibited the expression of TLR4 and NF-κB on BECs and decreased the urine levels of IL-1β and IL-6 and urine leukocyte counts. TLF-II reduced SLC20A1 and Galectin-3 expressions and increased Rab27b expression. The co-localization of SLC20A1 and Rab27b with CFT073 was significantly reduced in the TLF-II group.

Conclusion

Collectively, innate immunity and bacterial escape from fusiform vesicles play important roles in UPEC-induced bladder infections. Our findings suggest that TLF-II combats UPEC-induced bladder infections by effectively mitigating bladder inflammation and preventing bacterial escape from fusiform vesicles into the cytoplasm. The findings suggest that TLF-II is a promising option for treating UTI and reducing its recurrence.

D-Mannose reduces cellular senescence and NLRP3/GasderminD/IL-1β-driven pyroptotic uroepithelial cell shedding in the murine bladder

Aging is a risk factor for disease via increased susceptibility to infection, decreased ability to maintain homeostasis, inefficiency in combating stress, and decreased regenerative capacity. Multiple diseases, including urinary tract infection (UTI), are more prevalent with age; however, the mechanisms underlying the impact of aging on the urinary tract mucosa and the correlation between aging and disease remain poorly understood. Here, we show that, relative to young (8-12 weeks) mice, the urothelium of aged (18-24 months) female mice accumulates large lysosomes with reduced acid phosphatase activity and decreased overall autophagic flux in the aged urothelium, indicative of compromised cellular homeostasis. Aged bladders also exhibit basal accumulation of reactive oxygen species (ROS) and a dampened redox response, implying heightened oxidative stress. Furthermore, we identify a canonical senescence-associated secretory phenotype (SASP) in the aged urothelium, along with continuous NLRP3-inflammasome- and Gasdermin-D-dependent pyroptotic cell death. Consequently, aged mice chronically exfoliate urothelial cells, further exacerbating age-related urothelial dysfunction. Upon infection with uropathogenic E. coli, aged mice harbor increased bacterial reservoirs and are more prone to spontaneous recurrent UTI. Finally, we discover that treatment with D-mannose, a natural bioactive monosaccharide, rescues autophagy flux, reverses the SASP, and mitigates ROS and NLRP3/Gasdermin/interleukin (IL)-1β-driven pyroptotic epithelial cell shedding in aged mice. Collectively, our results demonstrate that normal aging affects bladder physiology, with aging alone increasing baseline cellular stress and susceptibility to infection, and suggest that mannose supplementation could serve as a senotherapeutic to counter age-associated urothelial dysfunction.

Tolterodine ameliorates inflammatory response and ferroptosis against LPS in human bladder epithelial cells

Bacterial endotoxin lipopolysaccharide (LPS)-induced inflammatory response and ferroptosis play an important role in urinary tract infections. Tolterodine has been used as a urinary tract antispasmodic and anticholinergic agent. However, the effects of Tolterodine against LPS-induced insults in human bladder epithelial cells (hBECs) have not been reported before. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase release assays to determine the cell viability, reactive oxygen species (ROS) and malondialdehyde level detection were used to determine the level of oxidative stress, enzyme-linked immunosorbent assay and Western blot analysis were used to detect the protein level. In the current study, we found that Tolterodine ameliorated LPS-induced production of ROS and lipid oxidation in hBECs. Interestingly, Tolterodine inhibited the production of interleukin 6, interleukin-1β, and tumor necrosis factor α. Also, Tolterodine reduced the levels of Fe2+ and suppressed ferroptosis by reducing the levels of glutathione peroxidase 4, prostaglandin-endoperoxide synthase 2, and acyl-CoA synthetase long-chain family member 4 in LPS-challenged bladder epithelial cells. Mechanistically, it was shown that Tolterodine restored the nuclear factor E2-related factor 2 (Nrf2)/nuclear factor-κB signaling. Importantly, inhibition of Nrf2 with its specific inhibitor ML385 abolished the protective effects of Tolterodine in the inflammatory response and ferroptosis, suggesting that the effects of Tolterodine are mediated by Nrf2. Based on these findings, we conclude that Tolterodine might serve as a promising agent for the treatment of LPS-induced bladder inflammation.

Exosomes derived from bladder epithelial cells infected with uropathogenic Escherichia coli increase the severity of urinary tract infections (UTIs) by impairing macrophage function

Uropathogenic Escherichia coli (UPEC) is the primary causative agent of urinary tract infections (UTIs) in humans. Moreover, as one of the most common bacterial pathogens, UPEC imposes a substantial burden on healthcare systems worldwide. Epithelial cells and macrophages are two major components of the innate immune system, which play critical roles in defending the bladder against UPEC invasion. Yet, the routes of communication between these cells during UTI pathogenesis are still not fully understood. In the present study, we investigated the role of membrane-bound nanovesicles (exosomes) in the communication between bladder epithelial cells and macrophages during UPEC infection, using an array of techniques such as flow cytometry, miRNA profiling, RNA sequencing, and western blotting. Moreover, our in vitro findings were validated in a mouse model of UPEC-induced cystitis. We found that UPEC infection induced the bladder epithelial MB49 cell line to secrete large numbers of exosomes (MB49-U-Exo), which were efficiently absorbed by macrophages both in vivo and in vitro. Assimilation of MB49-U-Exo induced macrophages to produce proinflammatory cytokines, including tumor necrosis factor (TNF)α. Exposure of macrophages to MB49-U-Exo reduced their phagocytic activity (by downregulating the expression of phagocytosis-related genes) and increased their rate of apoptosis. Mechanistically, we showed that MB49-U-Exo were enriched in miR-18a-5p, which induced TNFα expression in macrophages by targeting PTEN and activating the MAPK/JNK signaling pathway. Moreover, administration of the exosome secretion inhibitor GW4869 or a TNFα-neutralizing antibody alleviated UPEC-mediated tissue damage in mice with UPEC-induced cystitis by reducing the bacterial burden of the bladder and dampening the associated inflammatory response. Collectively, these findings suggest that MB49-U-Exo regulate macrophage function in a way that exacerbates UPEC-mediated tissue impairment. Thus, targeting exosomal -release or TNFα signaling during UPEC infection may represent promising non-antibiotic strategies for treating UTIs.

A human urothelial microtissue model reveals shared colonization and survival strategies between uropathogens and commensals

Urinary tract infection is among the most common infections worldwide, typically studied in animals and cell lines with limited uropathogenic strains. Here, we assessed diverse bacterial species in a human urothelial microtissue model exhibiting full stratification, differentiation, innate epithelial responses, and urine tolerance. Several uropathogens invaded intracellularly, but also commensal Escherichia coli, suggesting that invasion is a shared survival strategy, not solely a virulence hallmark. The E. coli adhesin FimH was required for intracellular bacterial community formation, but not for invasion. Other shared lifestyles included filamentation (Gram-negatives), chaining (Gram-positives), and hijacking of exfoliating cells, while biofilm-like aggregates were formed mainly with Pseudomonas and Proteus. Urothelial cells expelled invasive bacteria in Rab-/LC3-decorated structures, while highly cytotoxic/invasive uropathogens, but not commensals, disrupted host barrier function and strongly induced exfoliation and cytokine production. Overall, this work highlights diverse species-/strain-specific infection strategies and corresponding host responses in a human urothelial microenvironment, providing insights at the microtissue, cell, and molecular level.

Deciphering the roles of aryl hydrocarbon receptor (AHR) in regulating carcinogenesis

Aryl hydrocarbon receptor (AHR) is a ligand-dependent receptor that belongs to the superfamily of basic helix-loop-helix (bHLH) transcription factors. The activation of the canonical AHR signaling pathway is known to induce the expression of cytochrome P450 enzymes, facilitating the detoxification metabolism in the human body. Additionally, AHR could interact with various signaling pathways such as epidermal growth factor receptor (EGFR), signal transducer and activator of transcription 3 (STAT3), hypoxia-inducible factor-1α (HIF-1α), nuclear factor ekappa B (NF-κβ), estrogen receptor (ER), and androgen receptor (AR) signaling pathways. Over the past 30 years, several studies have reported that various chemical, physical, or biological agents, such as tobacco, hydrocarbon compounds, industrial and agricultural chemical wastes, drugs, UV, viruses, and other toxins, could affect AHR expression or activity, promoting cancer development. Thus, it is valuable to overview how these factors regulate AHR-mediated carcinogenesis. Current findings have reported that many compounds could act as AHR ligands to drive the expressions of AHR-target genes, such as CYP1A1, CYP1B1, MMPs, and AXL, and other targets that exert a pro-proliferation or anti-apoptotic effect, like XIAP. Furthermore, some other physical and chemical agents, such as UV and 3-methylcholanthrene, could promote AHR signaling activities, increasing the signaling activities of a few oncogenic pathways, such as the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathways. Understanding how various factors regulate AHR-mediated carcinogenesis processes helps clinicians and scientists plan personalized therapeutic strategies to improve anti-cancer treatment efficacy. As many studies that have reported the roles of AHR in regulating carcinogenesis are preclinical or observational clinical studies that did not explore the detailed mechanisms of how different chemical, physical, or biological agents promote AHR-mediated carcinogenesis processes, future studies should focus on conducting large-scale and functional studies to unravel the underlying mechanism of how AHR interacts with different factors in regulating carcinogenesis processes.

Roles of Oxidative Stress and Nrf2 Signaling in Pathogenic and Non-Pathogenic Cells: A Possible General Mechanism of Resistance to Therapy

The coordinating role of nuclear factor erythroid-2-related factor 2 (Nrf2) in cellular function is undeniable. Evidence indicates that this transcription factor exerts massive regulatory functions in multiple signaling pathways concerning redox homeostasis and xenobiotics, macromolecules, and iron metabolism. Being the master regulator of antioxidant system, Nrf2 controls cellular fate, influencing cell proliferation, differentiation, apoptosis, resistance to therapy, and senescence processes, as well as infection disease success. Because Nrf2 is the key coordinator of cell defence mechanisms, dysregulation of its signaling has been associated with carcinogenic phenomena and infectious and age-related diseases. Deregulation of this cytoprotective system may also interfere with immune response. Oxidative burst, one of the main microbicidal mechanisms, could be impaired during the initial phagocytosis of pathogens, which could lead to the successful establishment of infection and promote susceptibility to infectious diseases. There is still a knowledge gap to fill regarding the molecular mechanisms by which Nrf2 orchestrates such complex networks involving multiple pathways. This review describes the role of Nrf2 in non-pathogenic and pathogenic cells.

Multi-omic approach characterises the neuroprotective role of retromer in regulating lysosomal health

Retromer controls cellular homeostasis through regulating integral membrane protein sorting and transport and by controlling maturation of the endo-lysosomal network. Retromer dysfunction, which is linked to neurodegenerative disorders including Parkinson's and Alzheimer's diseases, manifests in complex cellular phenotypes, though the precise nature of this dysfunction, and its relation to neurodegeneration, remain unclear. Here, we perform an integrated multi-omics approach to provide precise insight into the impact of Retromer dysfunction on endo-lysosomal health and homeostasis within a human neuroglioma cell model. We quantify widespread changes to the lysosomal proteome, indicative of broad lysosomal dysfunction and inefficient autophagic lysosome reformation, coupled with a reconfigured cell surface proteome and secretome reflective of increased lysosomal exocytosis. Through this global proteomic approach and parallel transcriptomic analysis, we provide a holistic view of Retromer function in regulating lysosomal homeostasis and emphasise its role in neuroprotection.

Effects of aging on urinary tract epithelial homeostasis and immunity

A global increase in older individuals creates an increasing demand to understand numerous healthcare challenges related to aging. This population is subject to changes in tissue physiology and the immune response network. Older individuals are particularly susceptible to infectious diseases, with one of the most common being urinary tract infections (UTIs). Postmenopausal and older women have the highest risk of recurrent UTIs (rUTIs); however, why rUTIs become more frequent after menopause and during old age is incompletely understood. This increased susceptibility and severity among older individuals may involve functional changes to the immune system with age. Aging also has substantial effects on the epithelium and the immune system that led to impaired protection against pathogens, yet heightened and prolonged inflammation. How the immune system and its responses to infection changes within the bladder mucosa during aging has largely remained poorly understood. In this review, we highlight our understanding of bladder innate and adaptive immunity and the impact of aging and hormones and hormone therapy on bladder epithelial homeostasis and immunity. In particular, we elaborate on how the cellular and molecular immune landscape within the bladder can be altered during aging as aged mice develop bladder tertiary lymphoid tissues (bTLT), which are absent in young mice leading to profound age-associated change to the immune landscape in bladders that might drive the significant increase in UTI susceptibility. Knowledge of host factors that prevent or promote infection can lead to targeted treatment and prevention regimens. This review also identifies unique host factors to consider in the older, female host for improving rUTI treatment and prevention by dissecting the age-associated alteration of the bladder mucosal immune system.

Availability of Ferritin-Bound Iron to Enterobacteriaceae

The sequestration of iron in case of infection, termed nutritional immunity, is an established strategy of host defense. However, the interaction between pathogens and the mammalian iron storage protein ferritin is hitherto not completely understood. To better characterize the function of ferritin in Gram-negative infections, we incubated iron-starved cultures of Salmonella Typhimurium and knockout mutant strains defective for major iron uptake pathways or Escherichia coli with horse spleen ferritin or ionic iron as the sole iron source. Additionally, we added bovine superoxide dismutase and protease inhibitors to the growth medium to assess the effect of superoxide and bacterial proteases, respectively, on Salmonella proliferation and reductive iron release. Compared to free ionic iron, ferritin-bound iron was less available to Salmonella, but was still sufficient to significantly enhance the growth of the bacteria. In the absence of various iron acquisition genes, the availability of ferritin iron further decreased. Supplementation with superoxide dismutase significantly reduced the growth of the ΔentC knockout strain with holoferritin as the sole iron source in comparison with ionic ferrous iron. In contrast, this difference was not observed in the wildtype strain, suggesting that superoxide dismutase undermines bacterial iron uptake from ferritin by siderophore-independent mechanisms. Ferritin seems to diminish iron availability for bacteria in comparison to ionic iron, and its iron sequestering effect could possibly be enhanced by host superoxide dismutase activity.

The Use of Acute Immunosuppressive Therapy to Improve Antibiotic Efficacy against Intracellular Staphylococcus aureus

Interactions between Staphylococcus aureus and the host immune system can have significant impacts on antibiotic efficacy, suggesting that targeting and modulating the immune response to S. aureus infection may improve antibiotic efficacy and improve infection outcome. As we've previously shown, high levels of reactive oxygen species (ROS), associated with an M1-like proinflammatory macrophage response, potently induce antibiotic tolerance in S. aureus. Although the proinflammatory immune response is critical for initial control of pathogen burden, recent studies demonstrate that modulation of the macrophage response to an anti-inflammatory, or M2-like, response facilitates resolution of established S. aureus skin and soft tissue infections, arthritis, and bacteremia. Here, we evaluated the impact of host-directed immunosuppressive chemotherapeutics and anti-inflammatory agents on antibiotic efficacy against S. aureus. IMPORTANCE Staphylococcus aureus is the leading cause of hospital-acquired infections in the United States with high rates of antibiotic treatment failure. Macrophages represent an important intracellular niche in experimental models of S. aureus bacteremia. Although a proinflammatory macrophage response is critical for controlling infection, previous studies have identified an antagonistic relationship between antibiotic treatment and the proinflammatory macrophage response. Reactive oxygen species, produced by macrophages during respiratory burst, coerce S. aureus into an antibiotic tolerant state, leading to poor treatment outcome. Here, we aimed to determine the potential of host-directed immunomodulators that reduce the production of reactive oxygen species to improve antibiotic efficacy against intracellular S. aureus.

The urothelium: a multi-faceted barrier against a harsh environment

All mucosal surfaces must deal with the challenge of exposure to the outside world. The urothelium is a highly specialized layer of stratified epithelial cells lining the inner surface of the urinary bladder, a gruelling environment involving significant stretch forces, osmotic and hydrostatic pressures, toxic substances, and microbial invasion. The urinary bladder plays an important barrier role and allows the accommodation and expulsion of large volumes of urine without permitting urine components to diffuse across. The urothelium is made up of three cell types, basal, intermediate, and umbrella cells, whose specialized functions aid in the bladder's mission. In this review, we summarize the recent insights into urothelial structure, function, development, regeneration, and in particular the role of umbrella cells in barrier formation and maintenance. We briefly review diseases which involve the bladder and discuss current human urothelial in vitro models as a complement to traditional animal studies.

Timing is everything: impact of development, ageing and circadian rhythm on macrophage functions in urinary tract infections

The bladder supports a diversity of macrophage populations with functional roles related to homeostasis and host defense, including clearance of cell debris from tissue, immune surveillance, and inflammatory responses. This review examines these roles with particular attention given to macrophage origins, differentiation, recruitment, and engagement in host defense against urinary tract infections (UTIs), where these cells recognize uropathogens through a combination of receptor-mediated responses. Time is an important variable that is often overlooked in many clinical and biological studies, including in relation to macrophages and UTIs. Given that ageing is a significant factor in urinary tract infection pathogenesis and macrophages have been shown to harbor their own circadian system, this review also explores the influence of age on macrophage functions and the role of diurnal variations in macrophage functions in host defense and inflammation during UTIs. We provide a conceptual framework for future studies that address these key knowledge gaps.

PITing it forward: A new link in the journey of uropathogenic E. coli in the urothelium

Urinary tract infections (UTIs) are a cause for alarm given the high rates of treatment failure. In a recent issue of Cell Reports, Pang et al. uncovered dueling molecular machinery at the host-pathogen interface in response to phosphate that points to new anti-infective strategies against UTIs.

Bladder epithelial cell phosphate transporter inhibition protects mice against uropathogenic Escherichia coli infection

Urinary tract infections are predominantly caused by uropathogenic Escherichia coli (UPEC). UPEC infects bladder epithelial cells (BECs) via fusiform vesicles, escapes into the cytosol to evade exocytosis, and establishes intracellular bacterial communities (IBCs) for the next round of infection. The UPEC vesicle escape mechanism remains unclear. Here we show that UPEC senses host immune responses and initiates escape by upregulating a key phospholipase. The UPEC phospholipase PldA disrupts the vesicle membrane, and pldA expression is activated by phosphate reduction in vesicles. The host phosphate transporter PIT1 is located on the fusiform vesicle membrane, transporting phosphate into the cytosol. UPEC infection upregulates PIT1 via nuclear factor κB (NF-κB), resulting in phosphate reduction. Silencing PIT1 blocks UPEC vesicle escape in BECs, inhibits IBC formation in mouse bladders, and protects mice from UPEC infection. Our results shed light on pathogenic bacteria responding to intracellular phosphate shortage and tackling host defense and provide insights for development of new therapeutic agents to treat UPEC infection.