Biological Activities of Uric Acid in Infection Due to Enteropathogenic and Shiga-Toxigenic Escherichia coli

Abstract

In previous work, we identified xanthine oxidase (XO) as an important enzyme in the interaction between the host and enteropathogenic Escherichia coli (EPEC) and Shiga-toxigenic E. coli (STEC). Many of the biological effects of XO were due to the hydrogen peroxide produced by the enzyme. We wondered, however, if uric acid generated by XO also had biological effects in the gastrointestinal tract. Uric acid triggered inflammatory responses in the gut, including increased submucosal edema and release of extracellular DNA from host cells. While uric acid alone was unable to trigger a chloride secretory response in intestinal monolayers, it did potentiate the secretory response to cyclic AMP agonists. Uric acid crystals were formed in vivo in the lumen of the gut in response to EPEC and STEC infections. While trying to visualize uric acid crystals formed during EPEC and STEC infections, we noticed that uric acid crystals became enmeshed in the neutrophilic extracellular traps (NETs) produced from host cells in response to bacteria in cultured cell systems and in the intestine in vivo. Uric acid levels in the gut lumen increased in response to exogenous DNA, and these increases were enhanced by the actions of DNase I. Interestingly, addition of DNase I reduced the numbers of EPEC bacteria recovered after a 20-h infection and protected against EPEC-induced histologic damage. Xanthine oxidase (XO), also known as xanthine oxidoreductase (XOR), has been hailed as an important host defense against enteric pathogens for decades (1, 2). In a recent study, however, we found that XO could have deleterious as well as beneficial effects in the context of infection with Shiga-toxigenic Escherichia coli (STEC) (3). One of the deleterious effects of XO was its ability to induce production of the Shiga toxins (Stx) from STEC bacteria. Low to intermediate amounts of XO activity generated enough H 2 O 2 to induce Stx but not enough to actually kill STEC or enteropathogenic E. coli (EPEC) bacteria, resulting in an "uncanny valley" of worsened disease outcome.In addition to H 2 O 2 , XO also generates uric acid as a product. While uric acid used to be viewed as an inert waste product of purine metabolism, recent advances have highlighted the biological roles of uric acid in inflammation and innate immunity (4, 5). Although monosodium urate (MSU) is the technically more accurate term, we will use "uric acid" here, since the latter term is deeply entrenched in the biomedical literature. In a previous study, we found that uric acid crystals were formed in vivo in response to EPEC and STEC infection in the lumen of the gastrointestinal (GI) tract (6). In the present study, we focused on determining the biological effects of uric acid, as opposed to H 2 O 2 , produced by XO. We investigated the effects of uric acid on inflammatory responses, as well as secretory responses, in intestinal tissues and found that uric acid acted as a potentiator or modulator of proinflammatory or prosecretory agonists and that its crystals became enmeshed in the...

The emerging role of neutrophilic extracellular traps in intestinal disease

“…However, Crane et al . proposed that in the model of bacterial enteritis, NETs help enteropathogenic Escherichia coli (EPEC)and Shiga-like Escherichia coli (STEC)attach to the intestinal mucosa by enhancing the biofilm function of microorganisms [ 55 ]. These findings hint that NETs play a dual role in intestinal infections.…”

“…EPEC and STEC infections stimulate the formation of extracellular DNA NETs alonely NETs DNA DNase I NETs were acting as an non-antibacterial host defense. Additing DNase provided protection against the intestinal tissue damage caused by EPEC infection Crane et al [ 55 ] methicillin-resistant S. aureus (MRSA) Vivo(WT mice,NE −/− and PAD4 −/− mice Intravenous infection with MRSA, leading to rapid a neutrophil-dependent NET formation within the liver sinusoids ExtDNA、NE and histones DNase I Neutrophil recruitment and subsequent NET release destroyed the tight junction between endothelial cells and is associated with profound liver injury But the effectiveness of DNase might be limited in terms of removal of the most dangerous NET components and advocates for inhibition of NET production Elzbieta et al [ 56 ] Afa/Dr Diffusely Adhering Escherichia coli Vitro NET production by PLB-985 cells infected with the Afa/Dr wild-type (WT) E. coli strain C1845 NET-bound proteases DNase I NETs is actively involved in the antibacterial response of PLB-985 cells against enterovirulent WT C1845 bacteria. But PLB-985-derived NETs might directly contribute to Caco-2/TC7 epithelial cell damage via NET-bound proteases Marin-Esteban et al [ 57 ] Pseudomonas aeruginosa Vivo and vitro P. aeruginosa induces the production of NETs in vitro and in vivo and quickly responds and defends against the DNA and histone mediated-antibacterial effects of NETs by stabilizing the outer membrane ExtDNA DNase I, Mg 2+ and Ptase DNA backbone of NETs contributes to their bactericidal function.…”

Inflammatory response of uric acid produced by Porphyromonas gingivalis gingipains

“…Significant increases in XO activity in intestinal loop fluid and uric acid in serum have been detected in rabbits infected with EPEC and Shiga‐toxigenic E. coli (STEC) (Crane et al, 2013). In mice infected with EPEC and STEC, uric acid crystals formed in the mouse gut and became enmeshed in the DNA of neutrophil extracellular traps in vitro (Crane et al, 2016).…”

Netting Gut Disease: Neutrophil Extracellular Trap in Intestinal Pathology

“…The F-actin cytoskeletons of enterocyte-like cells were damaged in the presence of NETs. Crane et al [ 38 ] suggested that NETs could assist enteropathogenic Escherichia coli ( E.coli ) and Shiga-toxigenic E.coli to remain attached to the intestinal mucosa via DNA strands. These results have implied that NETs may benefit pathogens in the gut more than hurt them under some specific circumstance.…”