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Atg16L1 deficiency confers protection from uropathogenic Escherichia coli infection in vivo.

ABSTRACT: Urinary tract infection (UTI), a frequent and important disease in humans, is primarily caused by uropathogenic Escherichia coli (UPEC). UPEC forms acute cytoplasmic biofilms within superficial urothelial cells and can persist by establishing membrane-enclosed latent reservoirs to seed recurrent UTI. The host responds with an influx of innate immune cells and shedding of infected epithelial cells. The autophagy gene ATG16L1 has a commonly occurring mutation that is associated with inflammatory disease and intestinal cell abnormalities in mice and humans. Here, we show that Atg16L1-deficient mice (Atg16L1(HM)) cleared bacteriuria more rapidly and thoroughly than controls and showed rapid epithelial recovery. Atg16L1 deficiency was associated with a potent proinflammatory cytokine response with increased recruitment of monocytes and neutrophils to infected bladders. Chimeric and genetic studies showed that Atg16L1(HM) hematopoietic cells alone could increase clearance and that Atg16L1-deficient innate immune cells were required and sufficient for enhanced bacteriuric clearance. We also show that Atg16L1-deficient mice exhibit cell-autonomous architectural aberrations of superficial urothelial cells, including increases in multivesicular bodies, lysosomes, and expression of the UPEC receptor Up1a. Finally, we show that Atg16L1(HM) epithelial cells contained a significantly reduced number of latent reservoirs. Together, our results show that Atg16L1 deficiency confers protection in vivo to the host against both acute and latent UPEC infection, suggest that deficiency in a key autophagy protein can be protective against infection in an animal model of one of the most common diseases of women worldwide, and may have significant clinical implications for understanding the etiology of recurrent UTIs.

SUBMITTER: Wang C

PROVIDER: S-EPMC3390880 | biostudies-other | 2012 Jul

REPOSITORIES: biostudies-other

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Atg16L1 deficiency confers protection from uropathogenic Escherichia coli infection in vivo.

Wang Caihong C Mendonsa Graziella R GR Symington Jane W JW Zhang Qunyuan Q Cadwell Ken K Virgin Herbert W HW Mysorekar Indira U IU

Proceedings of the National Academy of Sciences of the United States of America 20120619 27

Urinary tract infection (UTI), a frequent and important disease in humans, is primarily caused by uropathogenic Escherichia coli (UPEC). UPEC forms acute cytoplasmic biofilms within superficial urothelial cells and can persist by establishing membrane-enclosed latent reservoirs to seed recurrent UTI. The host responds with an influx of innate immune cells and shedding of infected epithelial cells. The autophagy gene ATG16L1 has a commonly occurring mutation that is associated with inflammatory d ...[more]

PMID: 22715292

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Project description:To eradicate bacterial pathogens, neutrophils are recruited to the sites of infection, where they engulf and kill microbes through the production of reactive oxygen and chlorine species (ROS/RCS). The most prominent RCS is the antimicrobial oxidant hypochlorous acid (HOCl), which rapidly reacts with various amino acid side chains, including those containing sulfur and primary/tertiary amines, causing significant macromolecular damage. Pathogens like uropathogenic Escherichia coli (UPEC), the primary causative agent of urinary tract infections, have developed sophisticated defense systems to protect themselves from HOCl. We recently identified the RcrR regulon as a novel HOCl defense strategy in UPEC. Expression of the rcrARB operon is controlled by the HOCl-sensing transcriptional repressor RcrR, which is oxidatively inactivated by HOCl resulting in the expression of its target genes, including rcrB. The rcrB gene encodes a hypothetical membrane protein, deletion of which substantially increases UPEC's susceptibility to HOCl. However, the mechanism behind protection by RcrB is unclear. In this study, we investigated whether (i) its mode of action requires additional help, (ii) rcrARB expression is induced by physiologically relevant oxidants other than HOCl, and (iii) expression of this defense system is limited to specific media and/or cultivation conditions. We provide evidence that RcrB expression is sufficient to protect E. coli from HOCl. Furthermore, RcrB expression is induced by and protects from several RCS but not from ROS. RcrB plays a protective role for RCS-stressed planktonic cells under various growth and cultivation conditions but appears to be irrelevant for UPEC's biofilm formation. IMPORTANCE Bacterial infections pose an increasing threat to human health, exacerbating the demand for alternative treatments. Uropathogenic Escherichia coli (UPEC), the most common etiological agent of urinary tract infections (UTIs), are confronted by neutrophilic attacks in the bladder, and must therefore be equipped with powerful defense systems to fend off the toxic effects of reactive chlorine species. How UPEC deal with the negative consequences of the oxidative burst in the neutrophil phagosome remains unclear. Our study sheds light on the requirements for the expression and protective effects of RcrB, which we recently identified as UPEC's most potent defense system toward hypochlorous acid (HOCl) stress and phagocytosis. Thus, this novel HOCl stress defense system could potentially serve as an attractive drug target to increase the body's own capacity to fight UTIs.

Project description:Urinary tract infections (UTIs) afflict over 9 million women in America every year, often necessitating long-term prophylactic antibiotics. One risk factor for UTI is frequent sexual intercourse, which dramatically increases the risk of UTI. The mechanism behind this increased risk is unknown; however, bacteriuria increases immediately after sexual intercourse episodes, suggesting that physical manipulation introduces periurethral flora into the urinary tract. In this paper, we investigated whether superinfection (repeat introduction of bacteria) resulted in increased risk of severe UTI, manifesting as persistent bacteriuria, high titer bladder bacterial burdens and chronic inflammation, an outcome referred to as chronic cystitis. Chronic cystitis represents unchecked luminal bacterial replication and is defined histologically by urothelial hyperplasia and submucosal lymphoid aggregates, a histological pattern similar to that seen in humans suffering chronic UTI. C57BL/6J mice are resistant to chronic cystitis after a single infection; however, they developed persistent bacteriuria and chronic cystitis when superinfected 24 hours apart. Elevated levels of interleukin-6 (IL-6), keratinocyte cytokine (KC/CXCL1), and granulocyte colony-stimulating factor (G-CSF) in the serum of C57BL/6J mice prior to the second infection predicted the development of chronic cystitis. These same cytokines have been found to precede chronic cystitis in singly infected C3H/HeN mice. Furthermore, inoculating C3H/HeN mice twice within a six-hour period doubled the proportion of mice that developed chronic cystitis. Intracellular bacterial replication, regulated hemolysin (HlyA) expression, and caspase 1/11 activation were essential for this increase. Microarrays conducted at four weeks post inoculation in both mouse strains revealed upregulation of IL-1 and antimicrobial peptides during chronic cystitis. These data suggest a mechanism by which caspase-1/11 activation and IL-1 secretion could predispose certain women to recurrent UTI after frequent intercourse, a predisposition predictable by several serum biomarkers in two murine models.

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Atg16L1 deficiency confers protection from uropathogenic Escherichia coli infection in vivo.

Publications

Atg16L1 deficiency confers protection from uropathogenic Escherichia coli infection in vivo.

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