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Gardnerella vaginalis activates host responses necessary for Escherichia coli recurrent UTI from bladder reservoirs

ABSTRACT: Recurrent urinary tract infections (rUTI) are a costly clinical problem affecting millions of women worldwide each year. The majority of rUTI cases are caused by uropathogenic Escherichia coli (UPEC). Data from humans and mouse models indicate that some instances of rUTI are caused by UPEC emerging from latent reservoirs in the bladder. Some studies have reported that women with vaginal dysbiosis, typically characterized by high levels of Gardnerella vaginalis and other anaerobes, are at increased risk of UTI. Multiple studies have detected G. vaginalis in urine collected by transurethral catheterization (to limit vaginal contamination), suggesting that some women experience routine urinary tract exposures. We recently reported that inoculation of G. vaginalis into the bladder triggers rUTI from UPEC bladder reservoirs in a mouse model. Here we performed whole bladder RNAseq to identify host pathways involved in G. vaginalis-induced rUTI. We identified multiple host pathways differentially expressed following G. vaginalis exposure. At the gene and transcript level, we identified upregulation of the orphan nuclear receptor Nur77 (aka Nr4a1) and Nur77-regulated genes. Pilot data from Nur77 knockout mice suggests that Nur77 is necessary for G. vaganalis exposure to trigger rUTI.

ORGANISM(S): Mus musculus

PROVIDER: GSE186800 | GEO | 2021/11/01

REPOSITORIES: GEO

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Project description:The kidney and bladder expresses a variety of powerful defense mechanisms to limit urinary infection including iron scavenging, a process called "nutritional immunity". We previously demonstrated that bladder and kidney epithelia generates the archetype of the urinary iron defense, a lipocalin called NGAL which binds Enterochelin, a bacterial siderophore. However, because urinary bacteria can evade the bacteriostatic effects of NGAL by modifying Enterochelin and by producing additional siderophores, other mechanisms of "nutritional immunity" are anticipated. To study the defense in the kidney, we used a cell type specific method of RNA isolation in mouse (adapted from Gay et al, Oregon). A promiscuous form of phosphoribosyltransferase (UPRT) was cloned into the Rosa26 locus using a floxed-stop design which we activated in a cell specific fashion with Atp6v1b1-Cre. Thiouracil was introduced 12hr and 24hrs after urinary tract infection. Isolation of RNA directly from intercalated revealed synthetic (Npas1-Bmal1-Alas), transport (Hrg1, Flvcr1) and metabolic enzymes (Hmox1) of heme metabolism. Hmox1 was detected in the kidney with a luciferase based reporter (Contag et al, Stanford) after infection. CO production was detected in vivo and in AtpCre-mTmG FACS isolated intercalated cells in vitro using a novel metal-based probe synthesized at Columbia (adapted from Liu et al, China). Urinary bacteria (UPEC) with heme transport mutations were not competitive in the colonization of the kidney but conversely were markedly stimulated by iron, suggesting bacterial-host competition for heme capture and metabolism. In fact, infection upregulated both heme synthetic and metabolic genes, suggesting that CO production is induced by infection. Exposure to CO terminated the growth of UPEC. In sum, we have identified an unusual iron trafficking system in the collecting ducts that mirrors the nutritional requirements of UPEC to achieve pyelonephritis. Many of these components are specific to the intercalated cells, consistent with the notion that these cells defend the urinary tract from infection.

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Gardnerella vaginalis activates host responses necessary for Escherichia coli recurrent UTI from bladder reservoirs

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